1 /*
  2     Copyright 2008-2024
  3         Matthias Ehmann,
  4         Michael Gerhaeuser,
  5         Carsten Miller,
  6         Bianca Valentin,
  7         Alfred Wassermann,
  8         Peter Wilfahrt
  9 
 10     This file is part of JSXGraph.
 11 
 12     JSXGraph is free software dual licensed under the GNU LGPL or MIT License.
 13 
 14     You can redistribute it and/or modify it under the terms of the
 15 
 16       * GNU Lesser General Public License as published by
 17         the Free Software Foundation, either version 3 of the License, or
 18         (at your option) any later version
 19       OR
 20       * MIT License: https://github.com/jsxgraph/jsxgraph/blob/master/LICENSE.MIT
 21 
 22     JSXGraph is distributed in the hope that it will be useful,
 23     but WITHOUT ANY WARRANTY; without even the implied warranty of
 24     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 25     GNU Lesser General Public License for more details.
 26 
 27     You should have received a copy of the GNU Lesser General Public License and
 28     the MIT License along with JSXGraph. If not, see <https://www.gnu.org/licenses/>
 29     and <https://opensource.org/licenses/MIT/>.
 30  */
 31 
 32 /*global JXG: true, define: true*/
 33 /*jslint nomen: true, plusplus: true*/
 34 
 35 /**
 36  * @fileoverview This file contains our composition elements, i.e. these elements are mostly put together
 37  * from one or more {@link JXG.GeometryElement} but with a special meaning. E.g. the midpoint element is contained here
 38  * and this is just a {@link JXG.Point} with coordinates dependent from two other points. Currently in this file the
 39  * following compositions can be found: <ul>
 40  *   <li>{@link Arrowparallel} (currently private)</li>
 41  *   <li>{@link Bisector}</li>
 42  *   <li>{@link Msector}</li>
 43  *   <li>{@link Circumcircle}</li>
 44  *   <li>{@link Circumcirclemidpoint}</li>
 45  *   <li>{@link Integral}</li>
 46  *   <li>{@link Midpoint}</li>
 47  *   <li>{@link Mirrorpoint}</li>
 48  *   <li>{@link Normal}</li>
 49  *   <li>{@link Orthogonalprojection}</li>
 50  *   <li>{@link Parallel}</li>
 51  *   <li>{@link Perpendicular}</li>
 52  *   <li>{@link Perpendicularpoint}</li>
 53  *   <li>{@link Perpendicularsegment}</li>
 54  *   <li>{@link Reflection}</li></ul>
 55  */
 56 
 57 import JXG from "../jxg.js";
 58 import Mat from "../math/math.js";
 59 import Geometry from "../math/geometry.js";
 60 import Numerics from "../math/numerics.js";
 61 import Coords from "../base/coords.js";
 62 import Type from "../utils/type.js";
 63 import Const from "../base/constants.js";
 64 // import Point from "../base/point.js";
 65 // import Line from "../base/line.js";
 66 // import Circle from "../base/circle.js";
 67 // import Transform from "../base/transformation.js";
 68 import Composition from "../base/composition.js";
 69 // import Curve from "../base/curve.js";
 70 // import Polygon from "../base/polygon.js";
 71 
 72 /**
 73  * @class This is used to construct a point that is the orthogonal projection of a point to a line.
 74  * @pseudo
 75  * @description An orthogonal projection is given by a point and a line. It is determined by projecting the given point
 76  * orthogonal onto the given line.
 77  * @constructor
 78  * @name Orthogonalprojection
 79  * @type JXG.Point
 80  * @augments JXG.Point
 81  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
 82  * @param {JXG.Line_JXG.Point} p,l The constructed point is the orthogonal projection of p onto l.
 83  * @example
 84  * var p1 = board.create('point', [0.0, 4.0]);
 85  * var p2 = board.create('point', [6.0, 1.0]);
 86  * var l1 = board.create('line', [p1, p2]);
 87  * var p3 = board.create('point', [3.0, 3.0]);
 88  *
 89  * var pp1 = board.create('orthogonalprojection', [p3, l1]);
 90  * </pre><div class="jxgbox" id="JXG7708b215-39fa-41b6-b972-19d73d77d791" style="width: 400px; height: 400px;"></div>
 91  * <script type="text/javascript">
 92  *   var ppex1_board = JXG.JSXGraph.initBoard('JXG7708b215-39fa-41b6-b972-19d73d77d791', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
 93  *   var ppex1_p1 = ppex1_board.create('point', [0.0, 4.0]);
 94  *   var ppex1_p2 = ppex1_board.create('point', [6.0, 1.0]);
 95  *   var ppex1_l1 = ppex1_board.create('line', [ppex1_p1, ppex1_p2]);
 96  *   var ppex1_p3 = ppex1_board.create('point', [3.0, 3.0]);
 97  *   var ppex1_pp1 = ppex1_board.create('orthogonalprojection', [ppex1_p3, ppex1_l1]);
 98  * </script><pre>
 99  */
100 JXG.createOrthogonalProjection = function (board, parents, attributes) {
101     var l, p, t, attr;
102 
103     parents[0] = board.select(parents[0]);
104     parents[1] = board.select(parents[1]);
105 
106     if (
107         Type.isPointType(board, parents[0]) &&
108         parents[1].elementClass === Const.OBJECT_CLASS_LINE
109     ) {
110         p = Type.providePoints(board, [parents[0]], attributes, "point")[0];
111         l = parents[1];
112     } else if (
113         Type.isPointType(board, parents[1]) &&
114         parents[0].elementClass === Const.OBJECT_CLASS_LINE
115     ) {
116         p = Type.providePoints(board, [parents[1]], attributes, "point")[0];
117         l = parents[0];
118     } else {
119         throw new Error(
120             "JSXGraph: Can't create perpendicular point with parent types '" +
121                 typeof parents[0] +
122                 "' and '" +
123                 typeof parents[1] +
124                 "'." +
125                 "\nPossible parent types: [point,line]"
126         );
127     }
128 
129     attr = Type.copyAttributes(attributes, board.options, "orthogonalprojection");
130 
131     /**
132      * @type JXG.Element
133      * @ignore
134      */
135     t = board.create(
136         "point",
137         [
138             function () {
139                 return Geometry.projectPointToLine(p, l, board);
140             }
141         ],
142         attr
143     );
144 
145     if (Type.exists(p._is_new)) {
146         t.addChild(p);
147         delete p._is_new;
148     } else {
149         p.addChild(t);
150     }
151     l.addChild(t);
152 
153     t.elType = "orthogonalprojection";
154     t.setParents([p.id, t.id]);
155 
156     t.update();
157 
158     /**
159      * Used to generate a polynomial for the orthogonal projection
160      * @name Orthogonalprojection#generatePolynomial
161      * @returns {Array} An array containing the generated polynomial.
162      * @private
163      * @function
164      * @ignore
165      */
166     t.generatePolynomial = function () {
167         /*
168          *  Perpendicular takes point P and line L and creates point T and line M:
169          *
170          *                          | M
171          *                          |
172          *                          x P (p1,p2)
173          *                          |
174          *                          |
175          *  L                       |
176          *  ----------x-------------x------------------------x--------
177          *            A (a1,a2)     |T (t1,t2)               B (b1,b2)
178          *                          |
179          *                          |
180          *
181          * So we have two conditions:
182          *
183          *   (a)  AT  || TB          (collinearity condition)
184          *   (b)  PT _|_ AB          (orthogonality condition)
185          *
186          *      a2-t2       t2-b2
187          *     -------  =  -------           (1)
188          *      a1-t1       t1-b1
189          *
190          *      p2-t2         a1-b1
191          *     -------  =  - -------         (2)
192          *      p1-t1         a2-b2
193          *
194          * Multiplying (1) and (2) with denominators and simplifying gives
195          *
196          *    a2t1 - a2b1 + t2b1 - a1t2 + a1b2 - t1b2 = 0                  (1')
197          *
198          *    p2a2 - p2b2 - t2a2 + t2b2 + p1a1 - p1b1 - t1a1 + t1b1 = 0    (2')
199          *
200          */
201 
202         var a1 = l.point1.symbolic.x,
203             a2 = l.point1.symbolic.y,
204             b1 = l.point2.symbolic.x,
205             b2 = l.point2.symbolic.y,
206             p1 = p.symbolic.x,
207             p2 = p.symbolic.y,
208             t1 = t.symbolic.x,
209             t2 = t.symbolic.y,
210             poly1 = "(" + a2 + ")*(" + t1 + ")-(" + a2 + ")*(" + b1 + ")+(" + t2 + ")*(" + b1 + ")-(" + a1 + ")*(" + t2 + ")+(" + a1 + ")*(" +
211                 b2 + ")-(" + t1 + ")*(" + b2 + ")",
212             poly2 = "(" + p2 + ")*(" + a2 + ")-(" + p2 + ")*(" + b2 + ")-(" + t2 + ")*(" + a2 + ")+(" + t2 + ")*(" + b2 + ")+(" + p1 + ")*(" +
213                 a1 + ")-(" + p1 + ")*(" + b1 + ")-(" + t1 + ")*(" + a1 + ")+(" + t1 + ")*(" + b1 + ")";
214 
215         return [poly1, poly2];
216     };
217 
218     return t;
219 };
220 
221 /**
222 
223      * @class This element is used to provide a constructor for a perpendicular.
224      * @pseudo
225      * @description  A perpendicular is a composition of two elements: a line and a point. The line is orthogonal
226      * to a given line and contains a given point.
227      * @name Perpendicular
228      * @constructor
229      * @type JXG.Line
230      * @augments Segment
231      * @returns A {@link JXG.Line} object through the given point that is orthogonal to the given line.
232      * @throws {Error} If the elements cannot be constructed with the given parent objects an exception is thrown.
233      * @param {JXG.Line_JXG.Point} l,p The perpendicular line will be orthogonal to l and
234      * will contain p.
235      * @example
236      * // Create a perpendicular
237      * var p1 = board.create('point', [0.0, 2.0]);
238      * var p2 = board.create('point', [2.0, 1.0]);
239      * var l1 = board.create('line', [p1, p2]);
240      *
241      * var p3 = board.create('point', [3.0, 3.0]);
242      * var perp1 = board.create('perpendicular', [l1, p3]);
243      * </pre><div class="jxgbox" id="JXGd5b78842-7b27-4d37-b608-d02519e6cd03" style="width: 400px; height: 400px;"></div>
244      * <script type="text/javascript">
245      *   var pex1_board = JXG.JSXGraph.initBoard('JXGd5b78842-7b27-4d37-b608-d02519e6cd03', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
246      *   var pex1_p1 = pex1_board.create('point', [0.0, 2.0]);
247      *   var pex1_p2 = pex1_board.create('point', [2.0, 1.0]);
248      *   var pex1_l1 = pex1_board.create('line', [pex1_p1, pex1_p2]);
249      *   var pex1_p3 = pex1_board.create('point', [3.0, 3.0]);
250      *   var pex1_perp1 = pex1_board.create('perpendicular', [pex1_l1, pex1_p3]);
251      * </script><pre>
252      */
253 JXG.createPerpendicular = function (board, parents, attributes) {
254     var p, l, pd, attr;
255 
256     parents[0] = board.select(parents[0]);
257     parents[1] = board.select(parents[1]);
258 
259     if (
260         Type.isPointType(board, parents[0]) &&
261         parents[1].elementClass === Const.OBJECT_CLASS_LINE
262     ) {
263         l = parents[1];
264         p = Type.providePoints(board, [parents[0]], attributes, "point")[0];
265     } else if (
266         Type.isPointType(board, parents[1]) &&
267         parents[0].elementClass === Const.OBJECT_CLASS_LINE
268     ) {
269         l = parents[0];
270         p = Type.providePoints(board, [parents[1]], attributes, "point")[0];
271     } else {
272         throw new Error(
273             "JSXGraph: Can't create perpendicular with parent types '" +
274                 typeof parents[0] +
275                 "' and '" +
276                 typeof parents[1] +
277                 "'." +
278                 "\nPossible parent types: [line,point]"
279         );
280     }
281 
282     attr = Type.copyAttributes(attributes, board.options, "perpendicular");
283     pd = JXG.createLine(
284         board,
285         [
286             function () {
287                 return l.stdform[2] * p.X() - l.stdform[1] * p.Y();
288             },
289             function () {
290                 return -l.stdform[2] * p.Z();
291             },
292             function () {
293                 return l.stdform[1] * p.Z();
294             }
295         ],
296         attr
297     );
298 
299     pd.elType = "perpendicular";
300     pd.setParents([l.id, p.id]);
301 
302     if (Type.exists(p._is_new)) {
303         pd.addChild(p);
304         delete p._is_new;
305     } else {
306         p.addChild(pd);
307     }
308     l.addChild(pd);
309 
310     return pd;
311 };
312 
313 /**
314  * @class This is used to construct a perpendicular point.
315  * @pseudo
316  * @description A perpendicular point is given by a point and a line. It is determined by projecting the given point
317  * orthogonal onto the given line. This element should be used in GEONExTReader only. All other applications should
318  * use orthogonal projection {@link Orthogonalprojection}.
319  * @constructor
320  * @name PerpendicularPoint
321  * @type JXG.Point
322  * @augments JXG.Point
323  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
324  * @param {JXG.Line_JXG.Point} p,l The constructed point is the orthogonal projection of p onto l.
325  * @example
326  * var p1 = board.create('point', [0.0, 4.0]);
327  * var p2 = board.create('point', [6.0, 1.0]);
328  * var l1 = board.create('line', [p1, p2]);
329  * var p3 = board.create('point', [3.0, 3.0]);
330  *
331  * var pp1 = board.create('perpendicularpoint', [p3, l1]);
332  * </pre><div class="jxgbox" id="JXGded148c9-3536-44c0-ab81-1bb8fa48f3f4" style="width: 400px; height: 400px;"></div>
333  * <script type="text/javascript">
334  *   var ppex1_board = JXG.JSXGraph.initBoard('JXGded148c9-3536-44c0-ab81-1bb8fa48f3f4', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
335  *   var ppex1_p1 = ppex1_board.create('point', [0.0, 4.0]);
336  *   var ppex1_p2 = ppex1_board.create('point', [6.0, 1.0]);
337  *   var ppex1_l1 = ppex1_board.create('line', [ppex1_p1, ppex1_p2]);
338  *   var ppex1_p3 = ppex1_board.create('point', [3.0, 3.0]);
339  *   var ppex1_pp1 = ppex1_board.create('perpendicularpoint', [ppex1_p3, ppex1_l1]);
340  * </script><pre>
341  */
342 JXG.createPerpendicularPoint = function (board, parents, attributes) {
343     var l, p, t;
344 
345     parents[0] = board.select(parents[0]);
346     parents[1] = board.select(parents[1]);
347     if (
348         Type.isPointType(board, parents[0]) &&
349         parents[1].elementClass === Const.OBJECT_CLASS_LINE
350     ) {
351         p = Type.providePoints(board, [parents[0]], attributes, "point")[0];
352         l = parents[1];
353     } else if (
354         Type.isPointType(board, parents[1]) &&
355         parents[0].elementClass === Const.OBJECT_CLASS_LINE
356     ) {
357         p = Type.providePoints(board, [parents[1]], attributes, "point")[0];
358         l = parents[0];
359     } else {
360         throw new Error(
361             "JSXGraph: Can't create perpendicular point with parent types '" +
362                 typeof parents[0] +
363                 "' and '" +
364                 typeof parents[1] +
365                 "'." +
366                 "\nPossible parent types: [point,line]"
367         );
368     }
369 
370     /**
371      * @class
372      * @ignore
373      */
374     t = board.create(
375         "point",
376         [
377             function () {
378                 return Geometry.perpendicular(l, p, board)[0];
379             }
380         ],
381         attributes
382     );
383 
384     if (Type.exists(p._is_new)) {
385         t.addChild(p);
386         delete p._is_new;
387     } else {
388         p.addChild(t);
389     }
390     l.addChild(t);
391 
392     t.elType = "perpendicularpoint";
393     t.setParents([p.id, l.id]);
394 
395     t.update();
396 
397     /**
398      * Used to generate a polynomial for the perpendicular point
399      * @name PerpendicularPoint#generatePolynomial
400      * @returns {Array} An array containing the generated polynomial.
401      * @private
402      * @function
403      * @ignore
404      */
405     t.generatePolynomial = function () {
406         /*
407          *  Perpendicular takes point P and line L and creates point T and line M:
408          *
409          *                          | M
410          *                          |
411          *                          x P (p1,p2)
412          *                          |
413          *                          |
414          *  L                       |
415          *  ----------x-------------x------------------------x--------
416          *            A (a1,a2)     |T (t1,t2)               B (b1,b2)
417          *                          |
418          *                          |
419          *
420          * So we have two conditions:
421          *
422          *   (a)  AT  || TB          (collinearity condition)
423          *   (b)  PT _|_ AB          (orthogonality condition)
424          *
425          *      a2-t2       t2-b2
426          *     -------  =  -------           (1)
427          *      a1-t1       t1-b1
428          *
429          *      p2-t2         a1-b1
430          *     -------  =  - -------         (2)
431          *      p1-t1         a2-b2
432          *
433          * Multiplying (1) and (2) with denominators and simplifying gives
434          *
435          *    a2t1 - a2b1 + t2b1 - a1t2 + a1b2 - t1b2 = 0                  (1')
436          *
437          *    p2a2 - p2b2 - t2a2 + t2b2 + p1a1 - p1b1 - t1a1 + t1b1 = 0    (2')
438          *
439          */
440         var a1 = l.point1.symbolic.x,
441             a2 = l.point1.symbolic.y,
442             b1 = l.point2.symbolic.x,
443             b2 = l.point2.symbolic.y,
444             p1 = p.symbolic.x,
445             p2 = p.symbolic.y,
446             t1 = t.symbolic.x,
447             t2 = t.symbolic.y,
448             poly1 = "(" + a2 + ")*(" + t1 + ")-(" + a2 + ")*(" + b1 + ")+(" + t2 + ")*(" + b1 + ")-(" + a1 + ")*(" + t2 + ")+(" + a1 + ")*(" + b2 + ")-(" + t1 +
449                 ")*(" + b2 + ")",
450             poly2 = "(" + p2 + ")*(" + a2 + ")-(" + p2 + ")*(" + b2 + ")-(" + t2 + ")*(" + a2 + ")+(" + t2 + ")*(" + b2 + ")+(" + p1 + ")*(" + a1 + ")-(" + p1 +
451                 ")*(" + b1 + ")-(" + t1 + ")*(" + a1 + ")+(" + t1 + ")*(" + b1 + ")";
452 
453         return [poly1, poly2];
454     };
455 
456     return t;
457 };
458 
459 /**
460  * @class This element is used to provide a constructor for a perpendicular segment.
461  * @pseudo
462  * @description  A perpendicular is a composition of two elements: a line segment and a point. The line segment is orthogonal
463  * to a given line and contains a given point and meets the given line in the perpendicular point.
464  * @name PerpendicularSegment
465  * @constructor
466  * @type JXG.Line
467  * @augments Segment
468  * @returns An array containing two elements: A {@link JXG.Line} object in the first component and a
469  * {@link JXG.Point} element in the second component. The line segment is orthogonal to the given line and meets it
470  * in the returned point.
471  * @throws {Error} If the elements cannot be constructed with the given parent objects an exception is thrown.
472  * @param {JXG.Line_JXG.Point} l,p The perpendicular line will be orthogonal to l and
473  * will contain p. The perpendicular point is the intersection point of the two lines.
474  * @example
475  * // Create a perpendicular
476  * var p1 = board.create('point', [0.0, 2.0]);
477  * var p2 = board.create('point', [2.0, 1.0]);
478  * var l1 = board.create('line', [p1, p2]);
479  *
480  * var p3 = board.create('point', [3.0, 3.0]);
481  * var perp1 = board.create('perpendicularsegment', [l1, p3]);
482  * </pre><div class="jxgbox" id="JXG037a6eb2-781d-4b71-b286-763619a63f22" style="width: 400px; height: 400px;"></div>
483  * <script type="text/javascript">
484  *   var pex1_board = JXG.JSXGraph.initBoard('JXG037a6eb2-781d-4b71-b286-763619a63f22', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
485  *   var pex1_p1 = pex1_board.create('point', [0.0, 2.0]);
486  *   var pex1_p2 = pex1_board.create('point', [2.0, 1.0]);
487  *   var pex1_l1 = pex1_board.create('line', [pex1_p1, pex1_p2]);
488  *   var pex1_p3 = pex1_board.create('point', [3.0, 3.0]);
489  *   var pex1_perp1 = pex1_board.create('perpendicularsegment', [pex1_l1, pex1_p3]);
490  * </script><pre>
491  */
492 JXG.createPerpendicularSegment = function (board, parents, attributes) {
493     var p, l, pd, t, attr;
494 
495     parents[0] = board.select(parents[0]);
496     parents[1] = board.select(parents[1]);
497     if (
498         Type.isPointType(board, parents[0]) &&
499         parents[1].elementClass === Const.OBJECT_CLASS_LINE
500     ) {
501         l = parents[1];
502         p = Type.providePoints(board, [parents[0]], attributes, "point")[0];
503     } else if (
504         Type.isPointType(board, parents[1]) &&
505         parents[0].elementClass === Const.OBJECT_CLASS_LINE
506     ) {
507         l = parents[0];
508         p = Type.providePoints(board, [parents[1]], attributes, "point")[0];
509     } else {
510         throw new Error(
511             "JSXGraph: Can't create perpendicular with parent types '" +
512                 typeof parents[0] +
513                 "' and '" +
514                 typeof parents[1] +
515                 "'." +
516                 "\nPossible parent types: [line,point]"
517         );
518     }
519     attr = Type.copyAttributes(attributes, board.options, "perpendicularsegment", "point");
520     t = JXG.createPerpendicularPoint(board, [l, p], attr);
521     t.dump = false;
522 
523     if (!Type.exists(attributes.layer)) {
524         attributes.layer = board.options.layer.line;
525     }
526 
527     attr = Type.copyAttributes(attributes, board.options, "perpendicularsegment");
528     pd = JXG.createLine(
529         board,
530         [
531             function () {
532                 return Geometry.perpendicular(l, p, board)[1] ? [t, p] : [p, t];
533             }
534         ],
535         attr
536     );
537 
538     /**
539      * Helper point
540      * @memberOf PerpendicularSegment.prototype
541      * @type PerpendicularPoint
542      * @name point
543      */
544     pd.point = t;
545 
546     if (Type.exists(p._is_new)) {
547         pd.addChild(p);
548         delete p._is_new;
549     } else {
550         p.addChild(pd);
551     }
552     l.addChild(pd);
553 
554     pd.elType = "perpendicularsegment";
555     pd.setParents([p.id, l.id]);
556     pd.subs = {
557         point: t
558     };
559     pd.inherits.push(t);
560 
561     return pd;
562 };
563 
564 /**
565  * @class The midpoint element constructs a point in the middle of two given points.
566  * @pseudo
567  * @description A midpoint is given by two points. It is collinear to the given points and the distance
568  * is the same to each of the given points, i.e. it is in the middle of the given points.
569  * @constructor
570  * @name Midpoint
571  * @type JXG.Point
572  * @augments JXG.Point
573  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
574  * @param {JXG.Point_JXG.Point} p1,p2 The constructed point will be in the middle of p1 and p2.
575  * @param {JXG.Line} l The midpoint will be in the middle of {@link JXG.Line#point1} and {@link JXG.Line#point2} of
576  * the given line l.
577  * @example
578  * // Create base elements: 2 points and 1 line
579  * var p1 = board.create('point', [0.0, 2.0]);
580  * var p2 = board.create('point', [2.0, 1.0]);
581  * var l1 = board.create('segment', [[0.0, 3.0], [3.0, 3.0]]);
582  *
583  * var mp1 = board.create('midpoint', [p1, p2]);
584  * var mp2 = board.create('midpoint', [l1]);
585  * </pre><div class="jxgbox" id="JXG7927ef86-24ae-40cc-afb0-91ff61dd0de7" style="width: 400px; height: 400px;"></div>
586  * <script type="text/javascript">
587  *   var mpex1_board = JXG.JSXGraph.initBoard('JXG7927ef86-24ae-40cc-afb0-91ff61dd0de7', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
588  *   var mpex1_p1 = mpex1_board.create('point', [0.0, 2.0]);
589  *   var mpex1_p2 = mpex1_board.create('point', [2.0, 1.0]);
590  *   var mpex1_l1 = mpex1_board.create('segment', [[0.0, 3.0], [3.0, 3.0]]);
591  *   var mpex1_mp1 = mpex1_board.create('midpoint', [mpex1_p1, mpex1_p2]);
592  *   var mpex1_mp2 = mpex1_board.create('midpoint', [mpex1_l1]);
593  * </script><pre>
594  */
595 JXG.createMidpoint = function (board, parents, attributes) {
596     var a, b, t, i, attr;
597 
598     for (i = 0; i < parents.length; ++i) {
599         parents[i] = board.select(parents[i]);
600     }
601     if (
602         parents.length === 2 &&
603         Type.isPointType(board, parents[0]) &&
604         Type.isPointType(board, parents[1])
605     ) {
606         parents = Type.providePoints(board, parents, attributes, "point");
607         a = parents[0];
608         b = parents[1];
609     } else if (parents.length === 1 && parents[0].elementClass === Const.OBJECT_CLASS_LINE) {
610         a = parents[0].point1;
611         b = parents[0].point2;
612     } else {
613         throw new Error(
614             "JSXGraph: Can't create midpoint." +
615                 "\nPossible parent types: [point,point], [line]"
616         );
617     }
618 
619     attr = Type.copyAttributes(attributes, board.options, "midpoint");
620     /**
621      * @type JXG.Element
622      * @ignore
623      */
624     t = board.create(
625         "point",
626         [
627             function () {
628                 var x = a.coords.usrCoords[1] + b.coords.usrCoords[1];
629                 if (
630                     isNaN(x) ||
631                     Math.abs(a.coords.usrCoords[0]) < Mat.eps ||
632                     Math.abs(b.coords.usrCoords[0]) < Mat.eps
633                 ) {
634                     return NaN;
635                 }
636 
637                 return x * 0.5;
638             },
639             function () {
640                 var y = a.coords.usrCoords[2] + b.coords.usrCoords[2];
641                 if (
642                     isNaN(y) ||
643                     Math.abs(a.coords.usrCoords[0]) < Mat.eps ||
644                     Math.abs(b.coords.usrCoords[0]) < Mat.eps
645                 ) {
646                     return NaN;
647                 }
648 
649                 return y * 0.5;
650             }
651         ],
652         attr
653     );
654     if (Type.exists(a._is_new)) {
655         t.addChild(a);
656         delete a._is_new;
657     } else {
658         a.addChild(t);
659     }
660     if (Type.exists(b._is_new)) {
661         t.addChild(b);
662         delete b._is_new;
663     } else {
664         b.addChild(t);
665     }
666 
667     t.elType = "midpoint";
668     t.setParents([a.id, b.id]);
669 
670     t.prepareUpdate().update();
671 
672     /**
673      * Used to generate a polynomial for the midpoint.
674      * @name Midpoint#generatePolynomial
675      * @returns {Array} An array containing the generated polynomial.
676      * @private
677      * @function
678      * @ignore
679      */
680     t.generatePolynomial = function () {
681         /*
682          *  Midpoint takes two point A and B or line L (with points P and Q) and creates point T:
683          *
684          *  L (not necessarily)
685          *  ----------x------------------x------------------x--------
686          *            A (a1,a2)          T (t1,t2)          B (b1,b2)
687          *
688          * So we have two conditions:
689          *
690          *   (a)   AT  ||  TB           (collinearity condition)
691          *   (b)  [AT] == [TB]          (equidistant condition)
692          *
693          *      a2-t2       t2-b2
694          *     -------  =  -------                                         (1)
695          *      a1-t1       t1-b1
696          *
697          *     (a1 - t1)^2 + (a2 - t2)^2 = (b1 - t1)^2 + (b2 - t2)^2       (2)
698          *
699          *
700          * Multiplying (1) with denominators and simplifying (1) and (2) gives
701          *
702          *    a2t1 - a2b1 + t2b1 - a1t2 + a1b2 - t1b2 = 0                      (1')
703          *
704          *    a1^2 - 2a1t1 + a2^2 - 2a2t2 - b1^2 + 2b1t1 - b2^2 + 2b2t2 = 0    (2')
705          *
706          */
707         var a1 = a.symbolic.x,
708             a2 = a.symbolic.y,
709             b1 = b.symbolic.x,
710             b2 = b.symbolic.y,
711             t1 = t.symbolic.x,
712             t2 = t.symbolic.y,
713             poly1 = "(" + a2 + ")*(" + t1 + ")-(" + a2 + ")*(" + b1 + ")+(" + t2 + ")*(" + b1 + ")-(" + a1 + ")*(" + t2 + ")+(" + a1 + ")*(" + b2 +
714                 ")-(" + t1 + ")*(" + b2 + ")",
715             poly2 = "(" + a1 + ")^2 - 2*(" + a1 + ")*(" + t1 + ")+(" + a2 + ")^2-2*(" + a2 + ")*(" + t2 + ")-(" + b1 + ")^2+2*(" + b1 + ")*(" + t1 +
716                 ")-(" + b2 + ")^2+2*(" + b2 + ")*(" + t2 + ")";
717 
718         return [poly1, poly2];
719     };
720 
721     return t;
722 };
723 
724 /**
725  * @class This element is used to construct a parallel point.
726  * @pseudo
727  * @description A parallel point is given by three points. Taking the Euclidean vector from the first to the
728  * second point, the parallel point is determined by adding that vector to the third point.
729  * The line determined by the first two points is parallel to the line determined by the third point and the constructed point.
730  * @constructor
731  * @name Parallelpoint
732  * @type JXG.Point
733  * @augments JXG.Point
734  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
735  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 Taking the Euclidean vector <tt>v=p2-p1</tt> the parallel point is determined by
736  * <tt>p4 = p3+v</tt>
737  * @param {JXG.Line_JXG.Point} l,p The resulting point will together with p specify a line which is parallel to l.
738  * @example
739  * var p1 = board.create('point', [0.0, 2.0]);
740  * var p2 = board.create('point', [2.0, 1.0]);
741  * var p3 = board.create('point', [3.0, 3.0]);
742  *
743  * var pp1 = board.create('parallelpoint', [p1, p2, p3]);
744  * </pre><div class="jxgbox" id="JXG488c4be9-274f-40f0-a469-c5f70abe1f0e" style="width: 400px; height: 400px;"></div>
745  * <script type="text/javascript">
746  *   var ppex1_board = JXG.JSXGraph.initBoard('JXG488c4be9-274f-40f0-a469-c5f70abe1f0e', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
747  *   var ppex1_p1 = ppex1_board.create('point', [0.0, 2.0]);
748  *   var ppex1_p2 = ppex1_board.create('point', [2.0, 1.0]);
749  *   var ppex1_p3 = ppex1_board.create('point', [3.0, 3.0]);
750  *   var ppex1_pp1 = ppex1_board.create('parallelpoint', [ppex1_p1, ppex1_p2, ppex1_p3]);
751  * </script><pre>
752  */
753 JXG.createParallelPoint = function (board, parents, attributes) {
754     var a, b, c, p, i, attr;
755 
756     for (i = 0; i < parents.length; ++i) {
757         parents[i] = board.select(parents[i]);
758     }
759     if (
760         parents.length === 3 &&
761         Type.isPointType(board, parents[0]) &&
762         Type.isPointType(board, parents[1]) &&
763         Type.isPointType(board, parents[2])
764     ) {
765         parents = Type.providePoints(board, parents, attributes, "point");
766         a = parents[0];
767         b = parents[1];
768         c = parents[2];
769     } else if (
770         Type.isPointType(board, parents[0]) &&
771         parents[1].elementClass === Const.OBJECT_CLASS_LINE
772     ) {
773         c = Type.providePoints(board, [parents[0]], attributes, "point")[0];
774         a = parents[1].point1;
775         b = parents[1].point2;
776     } else if (
777         Type.isPointType(board, parents[1]) &&
778         parents[0].elementClass === Const.OBJECT_CLASS_LINE
779     ) {
780         c = Type.providePoints(board, [parents[1]], attributes, "point")[0];
781         a = parents[0].point1;
782         b = parents[0].point2;
783     } else {
784         throw new Error(
785             "JSXGraph: Can't create parallel point with parent types '" +
786                 typeof parents[0] +
787                 "', '" +
788                 typeof parents[1] +
789                 "' and '" +
790                 typeof parents[2] +
791                 "'." +
792                 "\nPossible parent types: [line,point], [point,point,point]"
793         );
794     }
795 
796     attr = Type.copyAttributes(attributes, board.options, 'parallelpoint');
797     /**
798      * @type {JXG.Element}
799      * @ignore
800      */
801     p = board.create(
802         "point",
803         [
804             function () {
805                 return c.coords.usrCoords[1] + b.coords.usrCoords[1] - a.coords.usrCoords[1];
806             },
807             function () {
808                 return c.coords.usrCoords[2] + b.coords.usrCoords[2] - a.coords.usrCoords[2];
809             }
810         ],
811         attr
812     );
813 
814     // required for algorithms requiring dependencies between elements
815     if (Type.exists(a._is_new)) {
816         p.addChild(a);
817         delete a._is_new;
818     } else {
819         a.addChild(p);
820     }
821     if (Type.exists(b._is_new)) {
822         p.addChild(b);
823         delete b._is_new;
824     } else {
825         b.addChild(p);
826     }
827     if (Type.exists(c._is_new)) {
828         p.addChild(c);
829         delete c._is_new;
830     } else {
831         c.addChild(p);
832     }
833 
834     p.elType = "parallelpoint";
835     p.setParents([a.id, b.id, c.id]);
836 
837     // required to set the coordinates because functions are considered as constraints. hence, the coordinates get set first after an update.
838     // can be removed if the above issue is resolved.
839     p.prepareUpdate().update();
840 
841     /**
842      * @function
843      * @ignore
844      */
845     p.generatePolynomial = function () {
846         /*
847          *  Parallelpoint takes three points A, B and C or line L (with points B and C) and creates point T:
848          *
849          *
850          *                     C (c1,c2)                             T (t1,t2)
851          *                      x                                     x
852          *                     /                                     /
853          *                    /                                     /
854          *                   /                                     /
855          *                  /                                     /
856          *                 /                                     /
857          *                /                                     /
858          *               /                                     /
859          *              /                                     /
860          *  L (opt)    /                                     /
861          *  ----------x-------------------------------------x--------
862          *            A (a1,a2)                             B (b1,b2)
863          *
864          * So we have two conditions:
865          *
866          *   (a)   CT  ||  AB           (collinearity condition I)
867          *   (b)   BT  ||  AC           (collinearity condition II)
868          *
869          * The corresponding equations are
870          *
871          *    (b2 - a2)(t1 - c1) - (t2 - c2)(b1 - a1) = 0         (1)
872          *    (t2 - b2)(a1 - c1) - (t1 - b1)(a2 - c2) = 0         (2)
873          *
874          * Simplifying (1) and (2) gives
875          *
876          *    b2t1 - b2c1 - a2t1 + a2c1 - t2b1 + t2a1 + c2b1 - c2a1 = 0      (1')
877          *    t2a1 - t2c1 - b2a1 + b2c1 - t1a2 + t1c2 + b1a2 - b1c2 = 0      (2')
878          *
879          */
880         var a1 = a.symbolic.x,
881             a2 = a.symbolic.y,
882             b1 = b.symbolic.x,
883             b2 = b.symbolic.y,
884             c1 = c.symbolic.x,
885             c2 = c.symbolic.y,
886             t1 = p.symbolic.x,
887             t2 = p.symbolic.y,
888             poly1 = "(" + b2 + ")*(" + t1 + ")-(" + b2 + ")*(" + c1 + ")-(" + a2 + ")*(" + t1 + ")+(" + a2 + ")*(" + c1 + ")-(" + t2 + ")*(" + b1 + ")+(" + t2 + ")*(" +
889                 a1 + ")+(" + c2 + ")*(" + b1 + ")-(" + c2 + ")*(" + a1 + ")",
890             poly2 = "(" + t2 + ")*(" + a1 + ")-(" + t2 + ")*(" + c1 + ")-(" + b2 + ")*(" + a1 + ")+(" + b2 + ")*(" + c1 + ")-(" + t1 + ")*(" + a2 + ")+(" + t1 + ")*(" +
891                 c2 + ")+(" + b1 + ")*(" + a2 + ")-(" + b1 + ")*(" + c2 + ")";
892 
893         return [poly1, poly2];
894     };
895 
896     return p;
897 };
898 
899 /**
900  * @class A parallel is a line through a given point with the same slope as a given line or
901  * the line through two given point.
902  * <p>
903  * If original line is given as a JSXGraph line object, the resulting parallel line will be defined by the given point and an
904  * infinitely far away point (an ideal point). That means, the line can not be shortened to a segment.
905  * <p>
906  * If the original line is given as two points, the resulting parallel line can be shortened to a a segment.
907  * @pseudo
908  * @name Parallel
909  * @augments Line
910  * @constructor
911  * @type JXG.Line
912  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
913  * @param {JXG.Line_JXG.Point} l,p The constructed line contains p and has the same slope as l. Alternative parameters are p1, p2, p: The
914  * constructed line contains p and has the same slope as the line through p1 and p2.
915  * @example
916  * // Create a parallel
917  * var p1 = board.create('point', [0.0, 2.0]);
918  * var p2 = board.create('point', [2.0, 1.0]);
919  * var l1 = board.create('line', [p1, p2]);
920  *
921  * var p3 = board.create('point', [3.0, 3.0]);
922  * var pl1 = board.create('parallel', [l1, p3]);
923  * </pre><div class="jxgbox" id="JXG24e54f9e-5c4e-4afb-9228-0ef27a59d627" style="width: 400px; height: 400px;"></div>
924  * <script type="text/javascript">
925  *   var plex1_board = JXG.JSXGraph.initBoard('JXG24e54f9e-5c4e-4afb-9228-0ef27a59d627', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
926  *   var plex1_p1 = plex1_board.create('point', [0.0, 2.0]);
927  *   var plex1_p2 = plex1_board.create('point', [2.0, 1.0]);
928  *   var plex1_l1 = plex1_board.create('line', [plex1_p1, plex1_p2]);
929  *   var plex1_p3 = plex1_board.create('point', [3.0, 3.0]);
930  *   var plex1_pl1 = plex1_board.create('parallel', [plex1_l1, plex1_p3]);
931  * </script><pre>
932  * @example
933  * var p1, p2, p3, l1, pl1;
934  *
935  * p1 = board.create('point', [0.0, 2.0]);
936  * p2 = board.create('point', [2.0, 1.0]);
937  * l1 = board.create('line', [p1, p2]);
938  *
939  * p3 = board.create('point', [1.0, 3.0]);
940  * pl1 = board.create('parallel', [p1, p2, p3], {straightFirst: false, straightLast: false});
941  *
942  * </pre><div id="JXGd643305d-20c3-4a88-91f9-8d0c4448594f" class="jxgbox" style="width: 300px; height: 300px;"></div>
943  * <script type="text/javascript">
944  *     (function() {
945  *         var board = JXG.JSXGraph.initBoard('JXGd643305d-20c3-4a88-91f9-8d0c4448594f',
946  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
947  *     var p1, p2, p3, l1, pl1;
948  *
949  *     p1 = board.create('point', [0.0, 2.0]);
950  *     p2 = board.create('point', [2.0, 1.0]);
951  *     l1 = board.create('line', [p1, p2]);
952  *
953  *     p3 = board.create('point', [1.0, 3.0]);
954  *     pl1 = board.create('parallel', [p1, p2, p3], {straightFirst: false, straightLast: false});
955  *
956  *     })();
957  *
958  * </script><pre>
959  *
960  */
961 JXG.createParallel = function (board, parents, attributes) {
962     var p,
963         pp,
964         pl,
965         li,
966         i,
967         attr,
968         ty = 1;
969 
970     for (i = 0; i < parents.length; ++i) {
971         parents[i] = board.select(parents[i]);
972     }
973     p = null;
974     if (parents.length === 3) {
975         // Line / segment through point parents[2] which is parallel to line through parents[0] and parents[1]
976         parents = Type.providePoints(board, parents, attributes, "point");
977         p = parents[2];
978         ty = 0;
979     } else if (Type.isPointType(board, parents[0])) {
980         // Parallel to line parents[1] through point parents[0]
981         p = Type.providePoints(board, [parents[0]], attributes, "point")[0];
982         /** @ignore */
983         li = function () {
984             return parents[1].stdform;
985         };
986     } else if (Type.isPointType(board, parents[1])) {
987         // Parallel to line parents[0] through point parents[1]
988         p = Type.providePoints(board, [parents[1]], attributes, "point")[0];
989         /** @ignore */
990         li = function () {
991             return parents[0].stdform;
992         };
993     }
994 
995     if (!Type.exists(attributes.layer)) {
996         attributes.layer = board.options.layer.line;
997     }
998 
999     attr = Type.copyAttributes(attributes, board.options, "parallel", "point");
1000     if (ty === 1) {
1001         // Line is given by line element. The parallel line is
1002         // constructed as line through an ideal point.
1003         pp = board.create(
1004             "point",
1005             [
1006                 function () {
1007                     return Mat.crossProduct([1, 0, 0], li());
1008                 }
1009             ],
1010             attr
1011         );
1012     } else {
1013         // Line is given by two points. The parallel line is
1014         // constructed as line through two finite point.
1015         pp = board.create("parallelpoint", parents, attr);
1016     }
1017     pp.isDraggable = true;
1018 
1019     attr = Type.copyAttributes(attributes, board.options, "parallel");
1020     // line creator also calls addChild
1021     pl = board.create("line", [p, pp], attr);
1022 
1023     pl.elType = "parallel";
1024     pl.subs = {
1025         point: pp
1026     };
1027 
1028     pl.inherits.push(pp);
1029     pl.setParents([parents[0].id, parents[1].id]);
1030     if (parents.length === 3) {
1031         pl.addParents(parents[2].id);
1032     }
1033 
1034     // p.addChild(pl);
1035 
1036     /**
1037      * Helper point used to create the parallel line. This point lies on the line at infinity, hence it's not visible,
1038      * not even with visible set to <tt>true</tt>. Creating another line through this point would make that other line
1039      * parallel to the create parallel.
1040      * @memberOf Parallel.prototype
1041      * @name point
1042      * @type JXG.Point
1043      */
1044     pl.point = pp;
1045 
1046     return pl;
1047 };
1048 
1049 /**
1050  * @class An arrow parallel is a segment with an arrow attached which is parallel through a given segment, given by its defining two points,
1051  * through a given point.
1052  * <p>
1053  * @pseudo
1054  * @constructor
1055  * @name Arrowparallel
1056  * @type Parallel
1057  * @augments Parallel
1058  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1059  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 The constructed arrow contains p3 and has the same slope as the line through p1 and p2.
1060  * @example
1061  * // Create a parallel
1062  * var p1 = board.create('point', [0.0, 2.0]);
1063  * var p2 = board.create('point', [2.0, 1.0]);
1064  * var l1 = board.create('segment', [p1, p2]);
1065  *
1066  * var p3 = board.create('point', [3.0, 3.0]);
1067  * var pl1 = board.create('arrowparallel', [p1, p2, p3]);
1068  * </pre><div class="jxgbox" id="JXGeeacdf99-036f-4e83-aeb6-f7388423e369" style="width: 400px; height: 400px;"></div>
1069  * <script type="text/javascript">
1070  * (function () {
1071  *   var plex1_board = JXG.JSXGraph.initBoard('JXGeeacdf99-036f-4e83-aeb6-f7388423e369', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1072  *   var plex1_p1 = plex1_board.create('point', [0.0, 2.0]);
1073  *   var plex1_p2 = plex1_board.create('point', [2.0, 1.0]);
1074  *   var plex1_l1 = plex1_board.create('segment', [plex1_p1, plex1_p2]);
1075  *   var plex1_p3 = plex1_board.create('point', [3.0, 3.0]);
1076  *   var plex1_pl1 = plex1_board.create('arrowparallel', [plex1_p1, plex1_p2, plex1_p3]);
1077  * })();
1078  * </script><pre>
1079  */
1080 JXG.createArrowParallel = function (board, parents, attributes) {
1081     var p, attr;
1082 
1083     /* parallel arrow point polynomials are done in createParallelPoint */
1084     try {
1085         attr = Type.copyAttributes(attributes, board.options, 'arrowparallel');
1086 
1087         if (attr.lastArrow === false) {
1088             // An arrow has to have an arrow head.
1089             attr.lastArrow = true;
1090         }
1091         p = JXG.createParallel(board, parents, attr).setAttribute({
1092             straightFirst: false,
1093             straightLast: false
1094         });
1095         p.type = Const.OBJECT_TYPE_VECTOR;
1096         p.elType = "arrowparallel";
1097 
1098         // parents are set in createParallel
1099 
1100         return p;
1101     } catch (e) {
1102         throw new Error(
1103             "JSXGraph: Can't create arrowparallel with parent types '" +
1104                 typeof parents[0] +
1105                 "' and '" +
1106                 typeof parents[1] +
1107                 "'." +
1108                 "\nPossible parent types: [line,point], [point,point,point]"
1109         );
1110     }
1111 };
1112 
1113 /**
1114  * @class A bisector is a line which divides an angle into two equal angles. It is given by three points A, B, and
1115  * C and divides the angle ABC into two equal sized parts.
1116  * @pseudo
1117  * @constructor
1118  * @name Bisector
1119  * @type JXG.Line
1120  * @augments JXG.Line
1121  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1122  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 The angle described by <tt>p1</tt>, <tt>p2</tt> and <tt>p3</tt> will
1123  * be divided into two equal angles.
1124  * @example
1125  * var p1 = board.create('point', [6.0, 4.0]);
1126  * var p2 = board.create('point', [3.0, 2.0]);
1127  * var p3 = board.create('point', [1.0, 7.0]);
1128  *
1129  * var bi1 = board.create('bisector', [p1, p2, p3]);
1130  * </pre><div class="jxgbox" id="JXG0d58cea8-b06a-407c-b27c-0908f508f5a4" style="width: 400px; height: 400px;"></div>
1131  * <script type="text/javascript">
1132  * (function () {
1133  *   var board = JXG.JSXGraph.initBoard('JXG0d58cea8-b06a-407c-b27c-0908f508f5a4', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1134  *   var p1 = board.create('point', [6.0, 4.0]);
1135  *   var p2 = board.create('point', [3.0, 2.0]);
1136  *   var p3 = board.create('point', [1.0, 7.0]);
1137  *   var bi1 = board.create('bisector', [p1, p2, p3]);
1138  * })();
1139  * </script><pre>
1140  */
1141 JXG.createBisector = function (board, parents, attributes) {
1142     var p, l, i, attr;
1143 
1144     parents = Type.providePoints(board, parents, attributes, "point");
1145     if (Type.isPoint(parents[0]) && Type.isPoint(parents[1]) && Type.isPoint(parents[2])) {
1146         // hidden and fixed helper
1147         attr = Type.copyAttributes(attributes, board.options, "bisector", "point");
1148         attr.snapToGrid = false;
1149 
1150         p = board.create(
1151             "point",
1152             [
1153                 function () {
1154                     return Geometry.angleBisector(parents[0], parents[1], parents[2], board);
1155                 }
1156             ],
1157             attr
1158         );
1159         p.dump = false;
1160 
1161         for (i = 0; i < 3; i++) {
1162             // required for algorithm requiring dependencies between elements
1163             if (Type.exists(parents[i]._is_new)) {
1164                 p.addChild(parents[i]);
1165                 delete parents[i]._is_new;
1166             } else {
1167                 parents[i].addChild(p);
1168             }
1169         }
1170 
1171         if (!Type.exists(attributes.layer)) {
1172             attributes.layer = board.options.layer.line;
1173         }
1174 
1175         attr = Type.copyAttributes(attributes, board.options, "bisector");
1176         l = JXG.createLine(board, [parents[1], p], attr);
1177 
1178         /**
1179          * Helper point
1180          * @memberOf Bisector.prototype
1181          * @type Point
1182          * @name point
1183          */
1184         l.point = p;
1185 
1186         l.elType = "bisector";
1187         l.setParents(parents);
1188         l.subs = {
1189             point: p
1190         };
1191         l.inherits.push(p);
1192 
1193         return l;
1194     }
1195 
1196     throw new Error(
1197         "JSXGraph: Can't create angle bisector with parent types '" +
1198             typeof parents[0] +
1199             "' and '" +
1200             typeof parents[1] +
1201             "'." +
1202             "\nPossible parent types: [point,point,point]"
1203     );
1204 };
1205 
1206 /**
1207  * @class Bisector lines are similar to {@link Bisector} but take two lines as parent elements. The resulting element is
1208  * a composition of two lines.
1209  * @pseudo
1210  * @constructor
1211  * @name Bisectorlines
1212  * @type JXG.Composition
1213  * @augments JXG.Composition
1214  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1215  * @param {JXG.Line_JXG.Line} l1,l2 The four angles described by the lines <tt>l1</tt> and <tt>l2</tt> will each
1216  * be divided into two equal angles.
1217  * @example
1218  * var p1 = board.create('point', [6.0, 4.0]);
1219  * var p2 = board.create('point', [3.0, 2.0]);
1220  * var p3 = board.create('point', [1.0, 7.0]);
1221  * var p4 = board.create('point', [3.0, 0.0]);
1222  * var l1 = board.create('line', [p1, p2]);
1223  * var l2 = board.create('line', [p3, p4]);
1224  *
1225  * var bi1 = board.create('bisectorlines', [l1, l2]);
1226  * </pre><div class="jxgbox" id="JXG3121ff67-44f0-4dda-bb10-9cda0b80bf18" style="width: 400px; height: 400px;"></div>
1227  * <script type="text/javascript">
1228  * (function () {
1229  *   var board = JXG.JSXGraph.initBoard('JXG3121ff67-44f0-4dda-bb10-9cda0b80bf18', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1230  *   var p1 = board.create('point', [6.0, 4.0]);
1231  *   var p2 = board.create('point', [3.0, 2.0]);
1232  *   var p3 = board.create('point', [1.0, 7.0]);
1233  *   var p4 = board.create('point', [3.0, 0.0]);
1234  *   var l1 = board.create('line', [p1, p2]);
1235  *   var l2 = board.create('line', [p3, p4]);
1236  *   var bi1 = board.create('bisectorlines', [l1, l2]);
1237  * })();
1238  * </script><pre>
1239  */
1240 JXG.createAngularBisectorsOfTwoLines = function (board, parents, attributes) {
1241     // The angular bisectors of two line [c1,a1,b1] and [c2,a2,b2] are determined by the equation:
1242     // (a1*x+b1*y+c1*z)/sqrt(a1^2+b1^2) = +/- (a2*x+b2*y+c2*z)/sqrt(a2^2+b2^2)
1243 
1244     var g1,
1245         g2,
1246         attr,
1247         ret,
1248         l1 = board.select(parents[0]),
1249         l2 = board.select(parents[1]);
1250 
1251     if (
1252         l1.elementClass !== Const.OBJECT_CLASS_LINE ||
1253         l2.elementClass !== Const.OBJECT_CLASS_LINE
1254     ) {
1255         throw new Error(
1256             "JSXGraph: Can't create angle bisectors of two lines with parent types '" +
1257                 typeof parents[0] +
1258                 "' and '" +
1259                 typeof parents[1] +
1260                 "'." +
1261                 "\nPossible parent types: [line,line]"
1262         );
1263     }
1264 
1265     if (!Type.exists(attributes.layer)) {
1266         attributes.layer = board.options.layer.line;
1267     }
1268 
1269     attr = Type.copyAttributes(attributes, board.options, "bisectorlines", "line1");
1270     g1 = board.create(
1271         "line",
1272         [
1273             function () {
1274                 var d1 = Mat.hypot(l1.stdform[1], l1.stdform[2]),
1275                     d2 = Mat.hypot(l2.stdform[1], l2.stdform[2]);
1276 
1277                 return l1.stdform[0] / d1 - l2.stdform[0] / d2;
1278             },
1279             function () {
1280                 var d1 = Mat.hypot(l1.stdform[1], l1.stdform[2]),
1281                     d2 = Mat.hypot(l2.stdform[1], l2.stdform[2]);
1282 
1283                 return l1.stdform[1] / d1 - l2.stdform[1] / d2;
1284             },
1285             function () {
1286                 var d1 = Mat.hypot(l1.stdform[1], l1.stdform[2]),
1287                     d2 = Mat.hypot(l2.stdform[1], l2.stdform[2]);
1288 
1289                 return l1.stdform[2] / d1 - l2.stdform[2] / d2;
1290             }
1291         ],
1292         attr
1293     );
1294 
1295     if (!Type.exists(attributes.layer)) {
1296         attributes.layer = board.options.layer.line;
1297     }
1298     attr = Type.copyAttributes(attributes, board.options, "bisectorlines", "line2");
1299     g2 = board.create(
1300         "line",
1301         [
1302             function () {
1303                 var d1 = Mat.hypot(l1.stdform[1], l1.stdform[2]),
1304                     d2 = Mat.hypot(l2.stdform[1], l2.stdform[2]);
1305 
1306                 return l1.stdform[0] / d1 + l2.stdform[0] / d2;
1307             },
1308             function () {
1309                 var d1 = Mat.hypot(l1.stdform[1], l1.stdform[2]),
1310                     d2 = Mat.hypot(l2.stdform[1], l2.stdform[2]);
1311 
1312                 return l1.stdform[1] / d1 + l2.stdform[1] / d2;
1313             },
1314             function () {
1315                 var d1 = Mat.hypot(l1.stdform[1], l1.stdform[2]),
1316                     d2 = Mat.hypot(l2.stdform[1], l2.stdform[2]);
1317 
1318                 return l1.stdform[2] / d1 + l2.stdform[2] / d2;
1319             }
1320         ],
1321         attr
1322     );
1323 
1324     // documentation
1325     /**
1326      * First line.
1327      * @memberOf Bisectorlines.prototype
1328      * @name line1
1329      * @type Line
1330      */
1331 
1332     /**
1333      * Second line.
1334      * @memberOf Bisectorlines.prototype
1335      * @name line2
1336      * @type Line
1337      */
1338 
1339     ret = new Composition({ line1: g1, line2: g2 });
1340 
1341     g1.dump = false;
1342     g2.dump = false;
1343 
1344     ret.elType = "bisectorlines";
1345     ret.setParents([l1.id, l2.id]);
1346     ret.subs = {
1347         line1: g1,
1348         line2: g2
1349     };
1350     // ret.inherits.push(g1, g2);
1351 
1352     return ret;
1353 };
1354 
1355 // /**
1356 //  * @class An m-sector is a line which divides an angle into two angles. It is given by three points A, B, and
1357 //  * C and a real number m, and divides an angle into two angles, an angle with amplitude m and an angle with
1358 //  * amplitude (1-m)
1359 //  * @pseudo
1360 //  * @constructor
1361 //  * @name Msector
1362 //  * @type JXG.Line
1363 //  * @augments JXG.Line
1364 //  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1365 //  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 The angle described by <tt>p1</tt>, <tt>p2</tt> and <tt>p3</tt> will
1366 //  * be divided into two angles according to the value of <tt>m</tt>.
1367 //  * @example
1368 //  * var p1 = board.create('point', [6.0, 4.0]);
1369 //  * var p2 = board.create('point', [3.0, 2.0]);
1370 //  * var p3 = board.create('point', [1.0, 7.0]);
1371 //  *
1372 //  * var bi1 = board.create('msector', [p1, p2, p3], 1/5);
1373 //  * </pre><div id="JXG0d58cea8-b06a-407c-b27c-0908f508f5a4" style="width: 400px; height: 400px;"></div>
1374 //  * <script type="text/javascript">
1375 //  * (function () {
1376 //  *   var board = JXG.JSXGraph.initBoard('JXG0d58cea8-b06a-407c-b27c-0908f508f5a4', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1377 //  *   var p1 = board.create('point', [6.0, 4.0]);
1378 //  *   var p2 = board.create('point', [3.0, 2.0]);
1379 //  *   var p3 = board.create('point', [1.0, 7.0]);
1380 //  *   var bi1 = board.create('msector', [p1, p2, p3], 1/5);
1381 //  * })();
1382 //  * </script><pre>
1383 //  */
1384 // JXG.createMsector = function (board, parents, attributes) {
1385 //     var p, l, i, attr;
1386 
1387 //     if (parents[0].elementClass === Const.OBJECT_CLASS_POINT &&
1388 //             parents[1].elementClass === Const.OBJECT_CLASS_POINT &&
1389 //             parents[2].elementClass === Const.OBJECT_CLASS_POINT) {
1390 //         // hidden and fixed helper
1391 //         attr = Type.copyAttributes(attributes, board.options, 'msector', 'point');
1392 //         p = board.create('point', [
1393 //             function () {
1394 //                 return Geometry.angleMsector(parents[0], parents[1], parents[2], parents[3], board);
1395 //             }
1396 //         ], attr);
1397 //         p.dump = false;
1398 
1399 //         for (i = 0; i < 3; i++) {
1400 //             // required for algorithm requiring dependencies between elements
1401 //             parents[i].addChild(p);
1402 //         }
1403 
1404 //         if (!Type.exists(attributes.layer)) {
1405 //             attributes.layer = board.options.layer.line;
1406 //         }
1407 
1408 //         attr = Type.copyAttributes(attributes, board.options, 'msector');
1409 //         l = JXG.createLine(board, [parents[1], p], attr);
1410 
1411 //         /**
1412 //          * Helper point
1413 //          * @memberOf Msector.prototype
1414 //          * @type Point
1415 //          * @name point
1416 //          */
1417 //         l.point = p;
1418 
1419 //         l.elType = 'msector';
1420 //         l.parents = [parents[0].id, parents[1].id, parents[2].id];
1421 //         l.subs = {
1422 //             point: p
1423 //         };
1424 //         l.inherits.push(p);
1425 
1426 //         return l;
1427 //     }
1428 
1429 //     throw new Error("JSXGraph: Can't create angle msector with parent types '" +
1430 //         (typeof parents[0]) + "' and '" + (typeof parents[1]) + "'." +
1431 //         "\nPossible parent types: [point,point,point,Number]");
1432 // };
1433 
1434 /**
1435  * @class Constructs the midpoint of a {@link Circumcircle}. Like the circumcircle the circumcenter
1436  * is constructed by providing three points.
1437  * @pseudo
1438  * @description A circumcenter is given by three points which are all lying on the circle with the
1439  * constructed circumcenter as the midpoint.
1440  * @constructor
1441  * @name Circumcenter
1442  * @type JXG.Point
1443  * @augments JXG.Point
1444  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1445  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 The constructed point is the midpoint of the circle determined
1446  * by p1, p2, and p3.
1447  * @example
1448  * var p1 = board.create('point', [0.0, 2.0]);
1449  * var p2 = board.create('point', [2.0, 1.0]);
1450  * var p3 = board.create('point', [3.0, 3.0]);
1451  *
1452  * var cc1 = board.create('circumcenter', [p1, p2, p3]);
1453  * </pre><div class="jxgbox" id="JXGe8a40f95-bf30-4eb4-88a8-f4d5495261fd" style="width: 400px; height: 400px;"></div>
1454  * <script type="text/javascript">
1455  *   var ccmex1_board = JXG.JSXGraph.initBoard('JXGe8a40f95-bf30-4eb4-88a8-f4d5495261fd', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1456  *   var ccmex1_p1 = ccmex1_board.create('point', [0.0, 2.0]);
1457  *   var ccmex1_p2 = ccmex1_board.create('point', [6.0, 1.0]);
1458  *   var ccmex1_p3 = ccmex1_board.create('point', [3.0, 7.0]);
1459  *   var ccmex1_cc1 = ccmex1_board.create('circumcenter', [ccmex1_p1, ccmex1_p2, ccmex1_p3]);
1460  * </script><pre>
1461  */
1462 JXG.createCircumcenter = function (board, parents, attributes) {
1463     var p, i, a, b, c;
1464 
1465     parents = Type.providePoints(board, parents, attributes, "point");
1466     if (Type.isPoint(parents[0]) && Type.isPoint(parents[1]) && Type.isPoint(parents[2])) {
1467         a = parents[0];
1468         b = parents[1];
1469         c = parents[2];
1470 
1471         p = JXG.createPoint(
1472             board,
1473             [
1474                 function () {
1475                     return Geometry.circumcenter(a, b, c, board);
1476                 }
1477             ],
1478             attributes
1479         );
1480 
1481         for (i = 0; i < 3; i++) {
1482             if (Type.exists(parents[i]._is_new)) {
1483                 p.addChild(parents[i]);
1484                 delete parents[i]._is_new;
1485             } else {
1486                 parents[i].addChild(p);
1487             }
1488         }
1489 
1490         p.elType = "circumcenter";
1491         p.setParents(parents);
1492 
1493         p.generatePolynomial = function () {
1494             /*
1495              *  CircumcircleMidpoint takes three points A, B and C  and creates point M, which is the circumcenter of A, B, and C.
1496              *
1497              *
1498              * So we have two conditions:
1499              *
1500              *   (a)   CT  ==  AT           (distance condition I)
1501              *   (b)   BT  ==  AT           (distance condition II)
1502              *
1503              */
1504             var a1 = a.symbolic.x,
1505                 a2 = a.symbolic.y,
1506                 b1 = b.symbolic.x,
1507                 b2 = b.symbolic.y,
1508                 c1 = c.symbolic.x,
1509                 c2 = c.symbolic.y,
1510                 t1 = p.symbolic.x,
1511                 t2 = p.symbolic.y,
1512                 poly1 = ["((", t1, ")-(", a1, "))^2+((", t2, ")-(", a2, "))^2-((", t1, ")-(", b1, "))^2-((", t2, ")-(", b2, "))^2"].join(""),
1513                 poly2 = ["((", t1, ")-(", a1, "))^2+((", t2, ")-(", a2, "))^2-((", t1, ")-(", c1, "))^2-((", t2, ")-(", c2, "))^2"].join("");
1514 
1515             return [poly1, poly2];
1516         };
1517 
1518         return p;
1519     }
1520 
1521     throw new Error(
1522         "JSXGraph: Can't create circumcircle midpoint with parent types '" +
1523             typeof parents[0] +
1524             "', '" +
1525             typeof parents[1] +
1526             "' and '" +
1527             typeof parents[2] +
1528             "'." +
1529             "\nPossible parent types: [point,point,point]"
1530     );
1531 };
1532 
1533 /**
1534  * @class Constructs the incenter of the triangle described by the three given points.
1535  * {@link https://mathworld.wolfram.com/Incenter.html}
1536  * @pseudo
1537  * @constructor
1538  * @name Incenter
1539  * @type JXG.Point
1540  * @augments JXG.Point
1541  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1542  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 The constructed point is the incenter of the triangle described
1543  * by p1, p2, and p3.
1544  * @example
1545  * var p1 = board.create('point', [0.0, 2.0]);
1546  * var p2 = board.create('point', [2.0, 1.0]);
1547  * var p3 = board.create('point', [3.0, 3.0]);
1548  *
1549  * var ic1 = board.create('incenter', [p1, p2, p3]);
1550  * </pre><div class="jxgbox" id="JXGe8a40f95-bf30-4eb4-88a8-a2d5495261fd" style="width: 400px; height: 400px;"></div>
1551  * <script type="text/javascript">
1552  *   var icmex1_board = JXG.JSXGraph.initBoard('JXGe8a40f95-bf30-4eb4-88a8-a2d5495261fd', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1553  *   var icmex1_p1 = icmex1_board.create('point', [0.0, 2.0]);
1554  *   var icmex1_p2 = icmex1_board.create('point', [6.0, 1.0]);
1555  *   var icmex1_p3 = icmex1_board.create('point', [3.0, 7.0]);
1556  *   var icmex1_ic1 = icmex1_board.create('incenter', [icmex1_p1, icmex1_p2, icmex1_p3]);
1557  * </script><pre>
1558  */
1559 JXG.createIncenter = function (board, parents, attributes) {
1560     var p, A, B, C, i;
1561 
1562     parents = Type.providePoints(board, parents, attributes, "point");
1563     if (
1564         parents.length >= 3 &&
1565         Type.isPoint(parents[0]) &&
1566         Type.isPoint(parents[1]) &&
1567         Type.isPoint(parents[2])
1568     ) {
1569         A = parents[0];
1570         B = parents[1];
1571         C = parents[2];
1572 
1573         p = board.create(
1574             "point",
1575             [
1576                 function () {
1577                     var a, b, c;
1578 
1579                     a = Mat.hypot(B.X() - C.X(), B.Y() - C.Y());
1580                     b = Mat.hypot(A.X() - C.X(), A.Y() - C.Y());
1581                     c = Mat.hypot(B.X() - A.X(), B.Y() - A.Y());
1582 
1583                     return new Coords(
1584                         Const.COORDS_BY_USER,
1585                         [
1586                             (a * A.X() + b * B.X() + c * C.X()) / (a + b + c),
1587                             (a * A.Y() + b * B.Y() + c * C.Y()) / (a + b + c)
1588                         ],
1589                         board
1590                     );
1591                 }
1592             ],
1593             attributes
1594         );
1595 
1596         for (i = 0; i < 3; i++) {
1597             if (Type.exists(parents[i]._is_new)) {
1598                 p.addChild(parents[i]);
1599                 delete parents[i]._is_new;
1600             } else {
1601                 parents[i].addChild(p);
1602             }
1603         }
1604 
1605         p.elType = "incenter";
1606         p.setParents(parents);
1607     } else {
1608         throw new Error(
1609             "JSXGraph: Can't create incenter with parent types '" +
1610                 typeof parents[0] +
1611                 "', '" +
1612                 typeof parents[1] +
1613                 "' and '" +
1614                 typeof parents[2] +
1615                 "'." +
1616                 "\nPossible parent types: [point,point,point]"
1617         );
1618     }
1619 
1620     return p;
1621 };
1622 
1623 /**
1624  * @class A circumcircle is given by three points which are all lying on the circle.
1625  * @pseudo
1626  * @constructor
1627  * @name Circumcircle
1628  * @type JXG.Circle
1629  * @augments JXG.Circle
1630  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1631  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 The constructed element is the circle determined by <tt>p1</tt>, <tt>p2</tt>, and <tt>p3</tt>.
1632  * @example
1633  * var p1 = board.create('point', [0.0, 2.0]);
1634  * var p2 = board.create('point', [2.0, 1.0]);
1635  * var p3 = board.create('point', [3.0, 3.0]);
1636  *
1637  * var cc1 = board.create('circumcircle', [p1, p2, p3]);
1638  * </pre><div class="jxgbox" id="JXGe65c9861-0bf0-402d-af57-3ab11962f5ac" style="width: 400px; height: 400px;"></div>
1639  * <script type="text/javascript">
1640  *   var ccex1_board = JXG.JSXGraph.initBoard('JXGe65c9861-0bf0-402d-af57-3ab11962f5ac', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1641  *   var ccex1_p1 = ccex1_board.create('point', [0.0, 2.0]);
1642  *   var ccex1_p2 = ccex1_board.create('point', [6.0, 1.0]);
1643  *   var ccex1_p3 = ccex1_board.create('point', [3.0, 7.0]);
1644  *   var ccex1_cc1 = ccex1_board.create('circumcircle', [ccex1_p1, ccex1_p2, ccex1_p3]);
1645  * </script><pre>
1646  */
1647 JXG.createCircumcircle = function (board, parents, attributes) {
1648     var p, c, attr, i;
1649 
1650     parents = Type.providePoints(board, parents, attributes, "point");
1651     if (parents === false) {
1652         throw new Error(
1653             "JSXGraph: Can't create circumcircle with parent types '" +
1654                 typeof parents[0] +
1655                 "', '" +
1656                 typeof parents[1] +
1657                 "' and '" +
1658                 typeof parents[2] +
1659                 "'." +
1660                 "\nPossible parent types: [point,point,point]"
1661         );
1662     }
1663 
1664     try {
1665         attr = Type.copyAttributes(attributes, board.options, "circumcircle", "center");
1666         p = JXG.createCircumcenter(board, parents, attr);
1667 
1668         p.dump = false;
1669 
1670         if (!Type.exists(attributes.layer)) {
1671             attributes.layer = board.options.layer.circle;
1672         }
1673         attr = Type.copyAttributes(attributes, board.options, "circumcircle");
1674         c = JXG.createCircle(board, [p, parents[0]], attr);
1675 
1676         c.elType = "circumcircle";
1677         c.setParents(parents);
1678         c.subs = {
1679             center: p
1680         };
1681         c.inherits.push(c);
1682         for (i = 0; i < 3; i++) {
1683             if (Type.exists(parents[i]._is_new)) {
1684                 c.addChild(parents[i]);
1685                 delete parents[i]._is_new;
1686             } else {
1687                 parents[i].addChild(c);
1688             }
1689         }
1690     } catch (e) {
1691         throw new Error(
1692             "JSXGraph: Can't create circumcircle with parent types '" +
1693                 typeof parents[0] +
1694                 "', '" +
1695                 typeof parents[1] +
1696                 "' and '" +
1697                 typeof parents[2] +
1698                 "'." +
1699                 "\nPossible parent types: [point,point,point]"
1700         );
1701     }
1702 
1703     // p is already stored as midpoint in c so there's no need to store it explicitly.
1704 
1705     return c;
1706 };
1707 
1708 /**
1709  * @class An incircle is given by three points.
1710  * @pseudo
1711  * @constructor
1712  * @name Incircle
1713  * @type JXG.Circle
1714  * @augments JXG.Circle
1715  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1716  * @param {JXG.Point_JXG.Point_JXG.Point} p1,p2,p3 The constructed point is the midpoint of the incircle of
1717  * <tt>p1</tt>, <tt>p2</tt>, and <tt>p3</tt>.
1718  * @example
1719  * var p1 = board.create('point', [0.0, 2.0]);
1720  * var p2 = board.create('point', [2.0, 1.0]);
1721  * var p3 = board.create('point', [3.0, 3.0]);
1722  *
1723  * var ic1 = board.create('incircle', [p1, p2, p3]);
1724  * </pre><div class="jxgbox" id="JXGe65c9861-0bf0-402d-af57-2ab12962f8ac" style="width: 400px; height: 400px;"></div>
1725  * <script type="text/javascript">
1726  *   var icex1_board = JXG.JSXGraph.initBoard('JXGe65c9861-0bf0-402d-af57-2ab12962f8ac', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1727  *   var icex1_p1 = icex1_board.create('point', [0.0, 2.0]);
1728  *   var icex1_p2 = icex1_board.create('point', [6.0, 1.0]);
1729  *   var icex1_p3 = icex1_board.create('point', [3.0, 7.0]);
1730  *   var icex1_ic1 = icex1_board.create('incircle', [icex1_p1, icex1_p2, icex1_p3]);
1731  * </script><pre>
1732  */
1733 JXG.createIncircle = function (board, parents, attributes) {
1734     var i, p, c, attr;
1735 
1736     parents = Type.providePoints(board, parents, attributes, "point");
1737     if (parents === false) {
1738         throw new Error(
1739             "JSXGraph: Can't create circumcircle with parent types '" +
1740                 typeof parents[0] +
1741                 "', '" +
1742                 typeof parents[1] +
1743                 "' and '" +
1744                 typeof parents[2] +
1745                 "'." +
1746                 "\nPossible parent types: [point,point,point]"
1747         );
1748     }
1749     try {
1750         attr = Type.copyAttributes(attributes, board.options, "incircle", "center");
1751         p = JXG.createIncenter(board, parents, attr);
1752 
1753         p.dump = false;
1754 
1755         if (!Type.exists(attributes.layer)) {
1756             attributes.layer = board.options.layer.circle;
1757         }
1758         attr = Type.copyAttributes(attributes, board.options, "incircle");
1759         c = JXG.createCircle(
1760             board,
1761             [
1762                 p,
1763                 function () {
1764                     var a = Mat.hypot(parents[1].X() - parents[2].X(), parents[1].Y() - parents[2].Y()),
1765                         b = Mat.hypot(parents[0].X() - parents[2].X(), parents[0].Y() - parents[2].Y()),
1766                         c = Mat.hypot(parents[1].X() - parents[0].X(), parents[1].Y() - parents[0].Y()),
1767                         s = (a + b + c) / 2;
1768 
1769                     return Math.sqrt(((s - a) * (s - b) * (s - c)) / s);
1770                 }
1771             ],
1772             attr
1773         );
1774 
1775         c.elType = "incircle";
1776         c.setParents(parents);
1777         for (i = 0; i < 3; i++) {
1778             if (Type.exists(parents[i]._is_new)) {
1779                 c.addChild(parents[i]);
1780                 delete parents[i]._is_new;
1781             } else {
1782                 parents[i].addChild(c);
1783             }
1784         }
1785 
1786         /**
1787          * The center of the incircle
1788          * @memberOf Incircle.prototype
1789          * @type Incenter
1790          * @name center
1791          */
1792         c.center = p;
1793 
1794         c.subs = {
1795             center: c.center
1796         };
1797         c.inherits.push(p);
1798     } catch (e) {
1799         throw new Error(
1800             "JSXGraph: Can't create circumcircle with parent types '" +
1801                 typeof parents[0] +
1802                 "', '" +
1803                 typeof parents[1] +
1804                 "' and '" +
1805                 typeof parents[2] +
1806                 "'." +
1807                 "\nPossible parent types: [point,point,point]"
1808         );
1809     }
1810 
1811     // p is already stored as midpoint in c so there's no need to store it explicitly.
1812 
1813     return c;
1814 };
1815 
1816 /**
1817  * @class This element is used to construct reflected elements (points, lines, circles, curves, polygons).
1818  * @pseudo
1819  * @description A reflected element (point, polygon, line or curve) is given by a given
1820  * object of the same type and a line of reflection.
1821  * It is determined by the reflection of the given element
1822  * across the given line.
1823  * @constructor
1824  * @name Reflection
1825  * @type JXG.GeometryElement
1826  * @augments JXG.GeometryElement
1827  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
1828  * @param {JXG.Point|JXG.Line|JXG.Curve|JXG.Polygon_JXG.Line} p,l The reflection element is the reflection of p across the line l.
1829  * @example
1830  * var p1 = board.create('point', [0.0, 4.0]);
1831  * var p2 = board.create('point', [6.0, 1.0]);
1832  * var l1 = board.create('line', [p1, p2]);
1833  * var p3 = board.create('point', [3.0, 3.0]);
1834  *
1835  * var rp1 = board.create('reflection', [p3, l1]);
1836  * </pre><div class="jxgbox" id="JXG087a798e-a36a-4f52-a2b4-29a23a69393b" style="width: 400px; height: 400px;"></div>
1837  * <script type="text/javascript">
1838  *   var rpex1_board = JXG.JSXGraph.initBoard('JXG087a798e-a36a-4f52-a2b4-29a23a69393b', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
1839  *   var rpex1_p1 = rpex1_board.create('point', [0.0, 4.0]);
1840  *   var rpex1_p2 = rpex1_board.create('point', [6.0, 1.0]);
1841  *   var rpex1_l1 = rpex1_board.create('line', [rpex1_p1, rpex1_p2]);
1842  *   var rpex1_p3 = rpex1_board.create('point', [3.0, 3.0]);
1843  *   var rpex1_rp1 = rpex1_board.create('reflection', [rpex1_p3, rpex1_l1]);
1844  * </script><pre>
1845  * @example
1846  *         // Reflection of more elements
1847  *         // reflection line
1848  *         var li = board.create('line', [1,1,1], {strokeColor: '#aaaaaa'});
1849  *
1850  *         var p1 = board.create('point', [-3,-1], {name: "A"});
1851  *         var q1 = board.create('reflection', [p1, li], {name: "A'"});
1852  *
1853  *         var l1 = board.create('line', [1,-5,1]);
1854  *         var l2 = board.create('reflection', [l1, li]);
1855  *
1856  *         var cu1 = board.create('curve', [[-3, -3, -2.5, -3, -3, -2.5], [-3, -2, -2, -2, -2.5, -2.5]], {strokeWidth:3});
1857  *         var cu2 = board.create('reflection', [cu1, li], {strokeColor: 'red', strokeWidth:3});
1858  *
1859  *         var pol1 = board.create('polygon', [[-6,-3], [-4,-5], [-5,-1.5]]);
1860  *         var pol2 = board.create('reflection', [pol1, li]);
1861  *
1862  *         var c1 = board.create('circle', [[-2,-2], [-2, -1]]);
1863  *         var c2 = board.create('reflection', [c1, li]);
1864  *
1865  *         var a1 = board.create('arc', [[1, 1], [0, 1], [1, 0]], {strokeColor: 'red'});
1866  *         var a2 = board.create('reflection', [a1, li], {strokeColor: 'red'});
1867  *
1868  *         var s1 = board.create('sector', [[-3.5,-3], [-3.5, -2], [-3.5,-4]], {
1869  *                           anglePoint: {visible:true}, center: {visible: true}, radiusPoint: {visible: true},
1870  *                           fillColor: 'yellow', strokeColor: 'black'});
1871  *         var s2 = board.create('reflection', [s1, li], {fillColor: 'yellow', strokeColor: 'black', fillOpacity: 0.5});
1872  *
1873  *         var an1 = board.create('angle', [[-4,3.9], [-3, 4], [-3, 3]]);
1874  *         var an2 = board.create('reflection', [an1, li]);
1875  *
1876  * </pre><div id="JXG8f763af4-d449-11e7-93b3-901b0e1b8723" class="jxgbox" style="width: 300px; height: 300px;"></div>
1877  * <script type="text/javascript">
1878  *     (function() {
1879  *         var board = JXG.JSXGraph.initBoard('JXG8f763af4-d449-11e7-93b3-901b0e1b8723',
1880  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
1881  *             // reflection line
1882  *             var li = board.create('line', [1,1,1], {strokeColor: '#aaaaaa'});
1883  *
1884  *             var p1 = board.create('point', [-3,-1], {name: "A"});
1885  *             var q1 = board.create('reflection', [p1, li], {name: "A'"});
1886  *
1887  *             var l1 = board.create('line', [1,-5,1]);
1888  *             var l2 = board.create('reflection', [l1, li]);
1889  *
1890  *             var cu1 = board.create('curve', [[-3, -3, -2.5, -3, -3, -2.5], [-3, -2, -2, -2, -2.5, -2.5]], {strokeWidth:3});
1891  *             var cu2 = board.create('reflection', [cu1, li], {strokeColor: 'red', strokeWidth:3});
1892  *
1893  *             var pol1 = board.create('polygon', [[-6,-3], [-4,-5], [-5,-1.5]]);
1894  *             var pol2 = board.create('reflection', [pol1, li]);
1895  *
1896  *             var c1 = board.create('circle', [[-2,-2], [-2, -1]]);
1897  *             var c2 = board.create('reflection', [c1, li]);
1898  *
1899  *         var a1 = board.create('arc', [[1, 1], [0, 1], [1, 0]], {strokeColor: 'red'});
1900  *         var a2 = board.create('reflection', [a1, li], {strokeColor: 'red'});
1901  *
1902  *         var s1 = board.create('sector', [[-3.5,-3], [-3.5, -2], [-3.5,-4]], {
1903  *                           anglePoint: {visible:true}, center: {visible: true}, radiusPoint: {visible: true},
1904  *                           fillColor: 'yellow', strokeColor: 'black'});
1905  *         var s2 = board.create('reflection', [s1, li], {fillColor: 'yellow', strokeColor: 'black', fillOpacity: 0.5});
1906  *
1907  *         var an1 = board.create('angle', [[-4,3.9], [-3, 4], [-3, 3]]);
1908  *         var an2 = board.create('reflection', [an1, li]);
1909  *
1910  *     })();
1911  *
1912  * </script><pre>
1913  *
1914  */
1915 JXG.createReflection = function (board, parents, attributes) {
1916     var l, org, r, r_c,
1917         t, i, attr, attr2,
1918         errStr = "\nPossible parent types: [point|line|curve|polygon|circle|arc|sector, line]";
1919 
1920     for (i = 0; i < parents.length; ++i) {
1921         parents[i] = board.select(parents[i]);
1922     }
1923 
1924     attr = Type.copyAttributes(attributes, board.options, "reflection");
1925 
1926     if (Type.isPoint(parents[0])) {
1927         org = Type.providePoints(board, [parents[0]], attr2)[0];
1928     } else if (
1929         parents[0].elementClass === Const.OBJECT_CLASS_CURVE ||
1930         parents[0].elementClass === Const.OBJECT_CLASS_LINE ||
1931         parents[0].type === Const.OBJECT_TYPE_POLYGON ||
1932         parents[0].elementClass === Const.OBJECT_CLASS_CIRCLE
1933     ) {
1934         org = parents[0];
1935     } else {
1936         throw new Error(
1937             "JSXGraph: Can't create reflection element with parent types '" +
1938                 typeof parents[0] +
1939                 "' and '" +
1940                 typeof parents[1] +
1941                 "'." +
1942                 errStr
1943         );
1944     }
1945 
1946     if (parents[1].elementClass === Const.OBJECT_CLASS_LINE) {
1947         l = parents[1];
1948     } else {
1949         throw new Error(
1950             "JSXGraph: Can't create reflected element with parent types '" +
1951                 typeof parents[0] +
1952                 "' and '" +
1953                 typeof parents[1] +
1954                 "'." +
1955                 errStr
1956         );
1957     }
1958     t = JXG.createTransform(board, [l], { type: "reflect" });
1959 
1960     if (Type.isPoint(org)) {
1961         r = JXG.createPoint(board, [org, t], attr);
1962 
1963         // Arcs and sectors are treated as curves
1964     } else if (org.elementClass === Const.OBJECT_CLASS_CURVE) {
1965         r = JXG.createCurve(board, [org, t], attr);
1966     } else if (org.elementClass === Const.OBJECT_CLASS_LINE) {
1967         r = JXG.createLine(board, [org, t], attr);
1968     } else if (org.type === Const.OBJECT_TYPE_POLYGON) {
1969         r = JXG.createPolygon(board, [org, t], attr);
1970     } else if (org.elementClass === Const.OBJECT_CLASS_CIRCLE) {
1971         if (attr.type.toLowerCase() === "euclidean") {
1972             // Create a circle element from a circle and a Euclidean transformation
1973             attr2 = Type.copyAttributes(attributes, board.options, "reflection", "center");
1974             r_c = JXG.createPoint(board, [org.center, t], attr2);
1975             r_c.prepareUpdate()
1976                 .update()
1977                 .updateVisibility(Type.evaluate(r_c.visProp.visible))
1978                 .updateRenderer();
1979             r = JXG.createCircle(
1980                 board,
1981                 [
1982                     r_c,
1983                     function () {
1984                         return org.Radius();
1985                     }
1986                 ],
1987                 attr
1988             );
1989         } else {
1990             // Create a conic element from a circle and a projective transformation
1991             r = JXG.createCircle(board, [org, t], attr);
1992         }
1993     } else {
1994         throw new Error(
1995             "JSXGraph: Can't create reflected element with parent types '" +
1996                 typeof parents[0] +
1997                 "' and '" +
1998                 typeof parents[1] +
1999                 "'." +
2000                 errStr
2001         );
2002     }
2003 
2004     if (Type.exists(org._is_new)) {
2005         r.addChild(org);
2006         delete org._is_new;
2007     } else {
2008         // org.addChild(r);
2009     }
2010     l.addChild(r);
2011 
2012     r.elType = "reflection";
2013     r.addParents(l);
2014     r.prepareUpdate().update(); //.updateVisibility(Type.evaluate(r.visProp.visible)).updateRenderer();
2015 
2016     if (Type.isPoint(r)) {
2017         r.generatePolynomial = function () {
2018             /*
2019              *  Reflection takes a point R and a line L and creates point P, which is the reflection of R on L.
2020              *  L is defined by two points A and B.
2021              *
2022              * So we have two conditions:
2023              *
2024              *   (a)   RP  _|_  AB            (orthogonality condition)
2025              *   (b)   AR  ==   AP            (distance condition)
2026              *
2027              */
2028             var a1 = l.point1.symbolic.x,
2029                 a2 = l.point1.symbolic.y,
2030                 b1 = l.point2.symbolic.x,
2031                 b2 = l.point2.symbolic.y,
2032                 p1 = org.symbolic.x,
2033                 p2 = org.symbolic.y,
2034                 r1 = r.symbolic.x,
2035                 r2 = r.symbolic.y,
2036                 poly1 = ["((", r2, ")-(", p2, "))*((", a2, ")-(", b2, "))+((", a1, ")-(", b1, "))*((", r1, ")-(", p1, "))"].join(""),
2037                 poly2 = ["((", r1, ")-(", a1, "))^2+((", r2, ")-(", a2, "))^2-((", p1, ")-(", a1, "))^2-((", p2, ")-(", a2, "))^2"].join("");
2038 
2039             return [poly1, poly2];
2040         };
2041     }
2042 
2043     return r;
2044 };
2045 
2046 /**
2047  * @class A mirror element of a point, line, circle, curve, polygon will be constructed.
2048  * @pseudo
2049  * @description A mirror element is determined by the reflection of a given point, line, circle, curve, polygon across another given point.
2050  * @constructor
2051  * @name mirrorelement
2052  * @type JXG.GeometryElement
2053  * @augments JXG.GeometryElement
2054  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
2055  * @param {JXG.Point|JXG.Line|JXG.Curve|JXG.Ppolygon_JXG.Point} p1,p2 The constructed element is the mirror image of p2 across p1.
2056  * @example
2057  *         // point of reflection
2058  *         var mirr = board.create('point', [-1,-1], {color: '#aaaaaa'});
2059  *
2060  *         var p1 = board.create('point', [-3,-1], {name: "A"});
2061  *         var q1 = board.create('mirrorelement', [p1, mirr], {name: "A'"});
2062  *
2063  *         var l1 = board.create('line', [1, -5, 1]);
2064  *         var l2 = board.create('mirrorelement', [l1, mirr]);
2065  *
2066  *         var cu1 = board.create('curve', [[-3, -3, -2.5, -3, -3, -2.5], [-3, -2, -2, -2, -2.5, -2.5]], {strokeWidth:3});
2067  *         var cu2 = board.create('mirrorelement', [cu1, mirr], {strokeColor: 'red', strokeWidth:3});
2068  *
2069  *         var pol1 = board.create('polygon', [[-6,-2], [-4,-4], [-5,-0.5]]);
2070  *         var pol2 = board.create('mirrorelement', [pol1, mirr]);
2071  *
2072  *         var c1 = board.create('circle', [[-6,-6], [-6, -5]]);
2073  *         var c2 = board.create('mirrorelement', [c1, mirr]);
2074  *
2075  *         var a1 = board.create('arc', [[1, 1], [0, 1], [1, 0]], {strokeColor: 'red'});
2076  *         var a2 = board.create('mirrorelement', [a1, mirr], {strokeColor: 'red'});
2077  *
2078  *         var s1 = board.create('sector', [[-3.5,-3], [-3.5, -2], [-3.5,-4]], {
2079  *                           anglePoint: {visible:true}, center: {visible: true}, radiusPoint: {visible: true},
2080  *                           fillColor: 'yellow', strokeColor: 'black'});
2081  *         var s2 = board.create('mirrorelement', [s1, mirr], {fillColor: 'yellow', strokeColor: 'black', fillOpacity: 0.5});
2082  *
2083  *         var an1 = board.create('angle', [[-4,3.9], [-3, 4], [-3, 3]]);
2084  *         var an2 = board.create('mirrorelement', [an1, mirr]);
2085  *
2086  *
2087  * </pre><div id="JXG026c779c-d8d9-11e7-93b3-901b0e1b8723" class="jxgbox" style="width: 300px; height: 300px;"></div>
2088  * <script type="text/javascript">
2089  *     (function() {
2090  *         var board = JXG.JSXGraph.initBoard('JXG026c779c-d8d9-11e7-93b3-901b0e1b8723',
2091  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2092  *             // point of reflection
2093  *             var mirr = board.create('point', [-1,-1], {color: '#aaaaaa'});
2094  *
2095  *             var p1 = board.create('point', [-3,-1], {name: "A"});
2096  *             var q1 = board.create('mirrorelement', [p1, mirr], {name: "A'"});
2097  *
2098  *             var l1 = board.create('line', [1,-5, 1]);
2099  *             var l2 = board.create('mirrorelement', [l1, mirr]);
2100  *
2101  *             var cu1 = board.create('curve', [[-3, -3, -2.5, -3, -3, -2.5], [-3, -2, -2, -2, -2.5, -2.5]], {strokeWidth:3});
2102  *             var cu2 = board.create('mirrorelement', [cu1, mirr], {strokeColor: 'red', strokeWidth:3});
2103  *
2104  *             var pol1 = board.create('polygon', [[-6,-2], [-4,-4], [-5,-0.5]]);
2105  *             var pol2 = board.create('mirrorelement', [pol1, mirr]);
2106  *
2107  *             var c1 = board.create('circle', [[-6,-6], [-6, -5]]);
2108  *             var c2 = board.create('mirrorelement', [c1, mirr]);
2109  *
2110  *         var a1 = board.create('arc', [[1, 1], [0, 1], [1, 0]], {strokeColor: 'red'});
2111  *         var a2 = board.create('mirrorelement', [a1, mirr], {strokeColor: 'red'});
2112  *
2113  *         var s1 = board.create('sector', [[-3.5,-3], [-3.5, -2], [-3.5,-4]], {
2114  *                           anglePoint: {visible:true}, center: {visible: true}, radiusPoint: {visible: true},
2115  *                           fillColor: 'yellow', strokeColor: 'black'});
2116  *         var s2 = board.create('mirrorelement', [s1, mirr], {fillColor: 'yellow', strokeColor: 'black', fillOpacity: 0.5});
2117  *
2118  *         var an1 = board.create('angle', [[-4,3.9], [-3, 4], [-3, 3]]);
2119  *         var an2 = board.create('mirrorelement', [an1, mirr]);
2120  *
2121  *     })();
2122  *
2123  * </script><pre>
2124  */
2125 JXG.createMirrorElement = function (board, parents, attributes) {
2126     var org, i, m, r, r_c, t,
2127         attr, attr2,
2128         errStr = "\nPossible parent types: [point|line|curve|polygon|circle|arc|sector, point]";
2129 
2130     for (i = 0; i < parents.length; ++i) {
2131         parents[i] = board.select(parents[i]);
2132     }
2133 
2134     attr = Type.copyAttributes(attributes, board.options, "mirrorelement");
2135     if (Type.isPoint(parents[0])) {
2136         // Create point to be mirrored if supplied by coords array.
2137         org = Type.providePoints(board, [parents[0]], attr)[0];
2138     } else if (
2139         parents[0].elementClass === Const.OBJECT_CLASS_CURVE ||
2140         parents[0].elementClass === Const.OBJECT_CLASS_LINE ||
2141         parents[0].type === Const.OBJECT_TYPE_POLYGON ||
2142         parents[0].elementClass === Const.OBJECT_CLASS_CIRCLE
2143     ) {
2144         org = parents[0];
2145     } else {
2146         throw new Error(
2147             "JSXGraph: Can't create mirror element with parent types '" +
2148                 typeof parents[0] +
2149                 "' and '" +
2150                 typeof parents[1] +
2151                 "'." +
2152                 errStr
2153         );
2154     }
2155 
2156     if (Type.isPoint(parents[1])) {
2157         attr2 = Type.copyAttributes(attributes, board.options, "mirrorelement", "point");
2158         // Create mirror point if supplied by coords array.
2159         m = Type.providePoints(board, [parents[1]], attr2)[0];
2160     } else {
2161         throw new Error(
2162             "JSXGraph: Can't create mirror element with parent types '" +
2163                 typeof parents[0] +
2164                 "' and '" +
2165                 typeof parents[1] +
2166                 "'." +
2167                 errStr
2168         );
2169     }
2170 
2171     t = JXG.createTransform(board, [Math.PI, m], { type: "rotate" });
2172     if (Type.isPoint(org)) {
2173         r = JXG.createPoint(board, [org, t], attr);
2174 
2175         // Arcs and sectors are treated as curves
2176     } else if (org.elementClass === Const.OBJECT_CLASS_CURVE) {
2177         r = JXG.createCurve(board, [org, t], attr);
2178     } else if (org.elementClass === Const.OBJECT_CLASS_LINE) {
2179         r = JXG.createLine(board, [org, t], attr);
2180     } else if (org.type === Const.OBJECT_TYPE_POLYGON) {
2181         r = JXG.createPolygon(board, [org, t], attr);
2182     } else if (org.elementClass === Const.OBJECT_CLASS_CIRCLE) {
2183         if (attr.type.toLowerCase() === "euclidean") {
2184             // Create a circle element from a circle and a Euclidean transformation
2185             attr2 = Type.copyAttributes(attributes, board.options, "mirrorelement", "center");
2186             r_c = JXG.createPoint(board, [org.center, t], attr2);
2187             r_c.prepareUpdate()
2188                 .update()
2189                 .updateVisibility(Type.evaluate(r_c.visProp.visible))
2190                 .updateRenderer();
2191             r = JXG.createCircle(
2192                 board,
2193                 [
2194                     r_c,
2195                     function () {
2196                         return org.Radius();
2197                     }
2198                 ],
2199                 attr
2200             );
2201         } else {
2202             // Create a conic element from a circle and a projective transformation
2203             r = JXG.createCircle(board, [org, t], attr);
2204         }
2205     } else {
2206         throw new Error(
2207             "JSXGraph: Can't create mirror element with parent types '" +
2208                 typeof parents[0] +
2209                 "' and '" +
2210                 typeof parents[1] +
2211                 "'." +
2212                 errStr
2213         );
2214     }
2215 
2216     if (Type.exists(org._is_new)) {
2217         r.addChild(org);
2218         delete org._is_new;
2219     } else {
2220         // org.addChild(r);
2221     }
2222     m.addChild(r);
2223 
2224     r.elType = "mirrorelement";
2225     r.addParents(m);
2226     r.prepareUpdate().update();
2227 
2228     return r;
2229 };
2230 
2231 /**
2232  * @class A mirror point will be constructed.
2233  * @pseudo
2234  * @description A mirror point is determined by the reflection of a given point against another given point.
2235  * @constructor
2236  * @name Mirrorpoint
2237  * @type JXG.Point
2238  * @augments JXG.Point
2239  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
2240  * @param {JXG.Point_JXG.Point} p1,p2 The constructed point is the reflection of p2 against p1.
2241  *
2242  * This method is superseeded by the more general {@link JXG.createMirrorElement}.
2243  * @example
2244  * var p1 = board.create('point', [3.0, 3.0]);
2245  * var p2 = board.create('point', [6.0, 1.0]);
2246  *
2247  * var mp1 = board.create('mirrorpoint', [p1, p2]);
2248  * </pre><div class="jxgbox" id="JXG7eb2a814-6c4b-4caa-8cfa-4183a948d25b" style="width: 400px; height: 400px;"></div>
2249  * <script type="text/javascript">
2250  *   var mpex1_board = JXG.JSXGraph.initBoard('JXG7eb2a814-6c4b-4caa-8cfa-4183a948d25b', {boundingbox: [-1, 9, 9, -1], axis: true, showcopyright: false, shownavigation: false});
2251  *   var mpex1_p1 = mpex1_board.create('point', [3.0, 3.0]);
2252  *   var mpex1_p2 = mpex1_board.create('point', [6.0, 1.0]);
2253  *   var mpex1_mp1 = mpex1_board.create('mirrorpoint', [mpex1_p1, mpex1_p2]);
2254  * </script><pre>
2255  */
2256 JXG.createMirrorPoint = function (board, parents, attributes) {
2257     var el = JXG.createMirrorElement(board, parents, attributes);
2258     el.elType = "mirrorpoint";
2259     return el;
2260 };
2261 
2262 /**
2263  * @class This element is used to visualize the integral of a given curve over a given interval.
2264  * @pseudo
2265  * @description The Integral element is used to visualize the area under a given curve over a given interval
2266  * and to calculate the area's value. For that a polygon and gliders are used. The polygon displays the area,
2267  * the gliders are used to change the interval dynamically.
2268  * @constructor
2269  * @name Integral
2270  * @type JXG.Curve
2271  * @augments JXG.Curve
2272  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
2273  * @param {Array_JXG.Curve} i,c The constructed element covers the area between the curve <tt>c</tt> and the x-axis
2274  * within the interval <tt>i</tt>.
2275  * @example
2276  * var c1 = board.create('functiongraph', [function (t) { return Math.cos(t)*t; }]);
2277  * var i1 = board.create('integral', [[-2.0, 2.0], c1]);
2278  * </pre><div class="jxgbox" id="JXGd45d7188-6624-4d6e-bebb-1efa2a305c8a" style="width: 400px; height: 400px;"></div>
2279  * <script type="text/javascript">
2280  *   var intex1_board = JXG.JSXGraph.initBoard('JXGd45d7188-6624-4d6e-bebb-1efa2a305c8a', {boundingbox: [-5, 5, 5, -5], axis: true, showcopyright: false, shownavigation: false});
2281  *   var intex1_c1 = intex1_board.create('functiongraph', [function (t) { return Math.cos(t)*t; }]);
2282  *   var intex1_i1 = intex1_board.create('integral', [[-2.0, 2.0], intex1_c1]);
2283  * </script><pre>
2284  */
2285 JXG.createIntegral = function (board, parents, attributes) {
2286     var interval, curve, attr, start, end,
2287         startx, starty, endx, endy,
2288         pa_on_curve, pa_on_axis, pb_on_curve, pb_on_axis,
2289         txt_fun,
2290         t = null, p;
2291 
2292     if (Type.isArray(parents[0]) && parents[1].elementClass === Const.OBJECT_CLASS_CURVE) {
2293         interval = parents[0];
2294         curve = parents[1];
2295     } else if (
2296         Type.isArray(parents[1]) &&
2297         parents[0].elementClass === Const.OBJECT_CLASS_CURVE
2298     ) {
2299         interval = parents[1];
2300         curve = parents[0];
2301     } else {
2302         throw new Error(
2303             "JSXGraph: Can't create integral with parent types '" +
2304                 typeof parents[0] +
2305                 "' and '" +
2306                 typeof parents[1] +
2307                 "'." +
2308                 "\nPossible parent types: [[number|function,number|function],curve]"
2309         );
2310     }
2311 
2312     attr = Type.copyAttributes(attributes, board.options, "integral");
2313     attr.withLabel = false; // There is a custom 'label' below.
2314     p = board.create("curve", [[0], [0]], attr);
2315 
2316     // Correct the interval if necessary - NOT ANYMORE, GGB's fault
2317     start = interval[0];
2318     end = interval[1];
2319 
2320     if (Type.isFunction(start)) {
2321         startx = start;
2322         starty = function () {
2323             return curve.Y(startx());
2324         };
2325         start = startx();
2326     } else {
2327         startx = start;
2328         starty = curve.Y(start);
2329     }
2330 
2331     if (Type.isFunction(end)) {
2332         endx = end;
2333         endy = function () {
2334             return curve.Y(endx());
2335         };
2336         end = endx();
2337     } else {
2338         endx = end;
2339         endy = curve.Y(end);
2340     }
2341 
2342     attr = Type.copyAttributes(attributes, board.options, "integral", "curveleft");
2343     pa_on_curve = board.create("glider", [startx, starty, curve], attr);
2344     if (Type.isFunction(startx)) {
2345         pa_on_curve.hideElement();
2346     }
2347 
2348     attr = Type.copyAttributes(attributes, board.options, 'integral', 'baseleft');
2349     pa_on_axis = board.create('point', [
2350             function () {
2351                 if (Type.evaluate(p.visProp.axis) === "y") {
2352                     return 0;
2353                 }
2354                 return pa_on_curve.X();
2355             },
2356             function () {
2357                 if (Type.evaluate(p.visProp.axis) === "y") {
2358                     return pa_on_curve.Y();
2359                 }
2360                 return 0;
2361             }
2362         ], attr);
2363 
2364     attr = Type.copyAttributes(attributes, board.options, "integral", "curveright");
2365     pb_on_curve = board.create("glider", [endx, endy, curve], attr);
2366     if (Type.isFunction(endx)) {
2367         pb_on_curve.hideElement();
2368     }
2369 
2370     attr = Type.copyAttributes(attributes, board.options, "integral", "baseright");
2371     pb_on_axis = board.create('point', [
2372             function () {
2373                 if (Type.evaluate(p.visProp.axis) === "y") {
2374                     return 0;
2375                 }
2376                 return pb_on_curve.X();
2377             },
2378             function () {
2379                 if (Type.evaluate(p.visProp.axis) === "y") {
2380                     return pb_on_curve.Y();
2381                 }
2382 
2383                 return 0;
2384             }
2385         ], attr);
2386 
2387     attr = Type.copyAttributes(attributes, board.options, "integral");
2388     if (attr.withlabel !== false && attr.axis !== "y") {
2389         attr = Type.copyAttributes(attributes, board.options, "integral", "label");
2390         attr = Type.copyAttributes(attr, board.options, "label");
2391 
2392         t = board.create('text', [
2393                 function () {
2394                     var off = new Coords(
2395                             Const.COORDS_BY_SCREEN,
2396                             [
2397                                 Type.evaluate(this.visProp.offset[0]) +
2398                                     this.board.origin.scrCoords[1],
2399                                 0
2400                             ],
2401                             this.board,
2402                             false
2403                         ),
2404                         bb = this.board.getBoundingBox(),
2405                         dx = (bb[2] - bb[0]) * 0.1,
2406                         x = pb_on_curve.X();
2407 
2408                     if (x < bb[0]) {
2409                         x = bb[0] + dx;
2410                     } else if (x > bb[2]) {
2411                         x = bb[2] - dx;
2412                     }
2413 
2414                     return x + off.usrCoords[1];
2415                 },
2416                 function () {
2417                     var off = new Coords(
2418                             Const.COORDS_BY_SCREEN,
2419                             [
2420                                 0,
2421                                 Type.evaluate(this.visProp.offset[1]) +
2422                                     this.board.origin.scrCoords[2]
2423                             ],
2424                             this.board,
2425                             false
2426                         ),
2427                         bb = this.board.getBoundingBox(),
2428                         dy = (bb[1] - bb[3]) * 0.1,
2429                         y = pb_on_curve.Y();
2430 
2431                     if (y > bb[1]) {
2432                         y = bb[1] - dy;
2433                     } else if (y < bb[3]) {
2434                         y = bb[3] + dy;
2435                     }
2436 
2437                     return y + off.usrCoords[2];
2438                 },
2439                 ''
2440             ], attr);
2441 
2442         txt_fun = function () {
2443             var Int = Numerics.NewtonCotes([pa_on_axis.X(), pb_on_axis.X()], curve.Y),
2444                 digits = Type.evaluate(t.visProp.digits),
2445                 val;
2446 
2447             if (t.useLocale()) {
2448                 val = t.formatNumberLocale(Int, digits);
2449             } else {
2450                 val = Type.toFixed(Int, digits);
2451             }
2452             return '∫ = ' + val;
2453         };
2454         t.setText(txt_fun);
2455         t.dump = false;
2456 
2457         pa_on_curve.addChild(t);
2458         pb_on_curve.addChild(t);
2459     }
2460 
2461     // dump stuff
2462     pa_on_curve.dump = false;
2463     pa_on_axis.dump = false;
2464 
2465     pb_on_curve.dump = false;
2466     pb_on_axis.dump = false;
2467 
2468     p.elType = "integral";
2469     p.setParents([curve.id, interval]);
2470     p.subs = {
2471         curveLeft: pa_on_curve,
2472         baseLeft: pa_on_axis,
2473         curveRight: pb_on_curve,
2474         baseRight: pb_on_axis
2475     };
2476     p.inherits.push(pa_on_curve, pa_on_axis, pb_on_curve, pb_on_axis);
2477 
2478     if (attr.withLabel) {
2479         p.subs.label = t;
2480         p.inherits.push(t);
2481     }
2482 
2483     /**
2484      * Returns the current value of the integral.
2485      * @memberOf Integral
2486      * @name Value
2487      * @function
2488      * @returns {Number}
2489      */
2490     p.Value = function () {
2491         return Numerics.I([pa_on_axis.X(), pb_on_axis.X()], curve.Y);
2492     };
2493 
2494     /**
2495      * documented in JXG.Curve
2496      * @class
2497      * @ignore
2498      */
2499     p.updateDataArray = function () {
2500         var x, y, i, left, right, lowx, upx, lowy, upy;
2501 
2502         if (Type.evaluate(this.visProp.axis) === "y") {
2503             if (pa_on_curve.Y() < pb_on_curve.Y()) {
2504                 lowx = pa_on_curve.X();
2505                 lowy = pa_on_curve.Y();
2506                 upx = pb_on_curve.X();
2507                 upy = pb_on_curve.Y();
2508             } else {
2509                 lowx = pb_on_curve.X();
2510                 lowy = pb_on_curve.Y();
2511                 upx = pa_on_curve.X();
2512                 upy = pa_on_curve.Y();
2513             }
2514             left = Math.min(lowx, upx);
2515             right = Math.max(lowx, upx);
2516 
2517             x = [0, lowx];
2518             y = [lowy, lowy];
2519 
2520             for (i = 0; i < curve.numberPoints; i++) {
2521                 if (
2522                     lowy <= curve.points[i].usrCoords[2] &&
2523                     left <= curve.points[i].usrCoords[1] &&
2524                     curve.points[i].usrCoords[2] <= upy &&
2525                     curve.points[i].usrCoords[1] <= right
2526                 ) {
2527                     x.push(curve.points[i].usrCoords[1]);
2528                     y.push(curve.points[i].usrCoords[2]);
2529                 }
2530             }
2531             x.push(upx);
2532             y.push(upy);
2533             x.push(0);
2534             y.push(upy);
2535 
2536             // close the curve
2537             x.push(0);
2538             y.push(lowy);
2539         } else {
2540             if (pa_on_axis.X() < pb_on_axis.X()) {
2541                 left = pa_on_axis.X();
2542                 right = pb_on_axis.X();
2543             } else {
2544                 left = pb_on_axis.X();
2545                 right = pa_on_axis.X();
2546             }
2547 
2548             x = [left, left];
2549             y = [0, curve.Y(left)];
2550 
2551             for (i = 0; i < curve.numberPoints; i++) {
2552                 if (
2553                     left <= curve.points[i].usrCoords[1] &&
2554                     curve.points[i].usrCoords[1] <= right
2555                 ) {
2556                     x.push(curve.points[i].usrCoords[1]);
2557                     y.push(curve.points[i].usrCoords[2]);
2558                 }
2559             }
2560             x.push(right);
2561             y.push(curve.Y(right));
2562             x.push(right);
2563             y.push(0);
2564 
2565             // close the curve
2566             x.push(left);
2567             y.push(0);
2568         }
2569 
2570         this.dataX = x;
2571         this.dataY = y;
2572     };
2573 
2574     pa_on_curve.addChild(p);
2575     pb_on_curve.addChild(p);
2576     pa_on_axis.addChild(p);
2577     pb_on_axis.addChild(p);
2578 
2579     /**
2580      * The point on the axis initially corresponding to the lower value of the interval.
2581      *
2582      * @name baseLeft
2583      * @memberOf Integral
2584      * @type JXG.Point
2585      */
2586     p.baseLeft = pa_on_axis;
2587 
2588     /**
2589      * The point on the axis initially corresponding to the higher value of the interval.
2590      *
2591      * @name baseRight
2592      * @memberOf Integral
2593      * @type JXG.Point
2594      */
2595     p.baseRight = pb_on_axis;
2596 
2597     /**
2598      * The glider on the curve corresponding to the lower value of the interval.
2599      *
2600      * @name curveLeft
2601      * @memberOf Integral
2602      * @type Glider
2603      */
2604     p.curveLeft = pa_on_curve;
2605 
2606     /**
2607      * The glider on the axis corresponding to the higher value of the interval.
2608      *
2609      * @name curveRight
2610      * @memberOf Integral
2611      * @type Glider
2612      */
2613     p.curveRight = pb_on_curve;
2614 
2615     p.methodMap = JXG.deepCopy(p.methodMap, {
2616         curveLeft: "curveLeft",
2617         baseLeft: "baseLeft",
2618         curveRight: "curveRight",
2619         baseRight: "baseRight",
2620         Value: "Value"
2621     });
2622 
2623     /**
2624      * documented in GeometryElement
2625      * @ignore
2626      */
2627     p.label = t;
2628 
2629     return p;
2630 };
2631 
2632 /**
2633  * @class Creates an area indicating the solution of a linear inequality or an inequality
2634  * of a function graph, i.e. an inequality of type y <= f(x).
2635  * @pseudo
2636  * @description Display the solution set of a linear inequality (less than or equal to).
2637  * To be precise, the solution set of the inequality <i>y <= b/a * x + c/a</i> is shown.
2638  * In case <i>a = 0</i>, that is if the equation of the line is <i>bx + c = 0</i>,
2639  * the area of the inequality <i>bx + c <= 0</i> is shown.
2640  * <p>
2641  * For function graphs the area below the function graph is filled, i.e. the
2642  * area of the inequality y <= f(x).
2643  * With the attribute inverse:true the area of the inequality y >= f(x) is filled.
2644  *
2645  * @param {JXG.Line} l The area drawn will be the area below this line. With the attribute
2646  * inverse:true, the inequality 'greater than or equal to' is shown.
2647  * @constructor
2648  * @name Inequality
2649  * @type JXG.Curve
2650  * @augments JXG.Curve
2651  * @throws {Error} If the element cannot be constructed with the given parent objects an exception is thrown.
2652  * @example
2653  * var p = board.create('point', [1, 3]),
2654  *     q = board.create('point', [-2, -4]),
2655  *     l = board.create('line', [p, q]),
2656  *     ineq = board.create('inequality', [l]);
2657  * ineq = board.create('inequality', [l]);
2658  * </pre><div class="jxgbox" id="JXG2b703006-fd98-11e1-b79e-ef9e591c002e" style="width: 400px; height: 400px;"></div>
2659  * <script type="text/javascript">
2660  * (function () {
2661  *  var board = JXG.JSXGraph.initBoard('JXG2b703006-fd98-11e1-b79e-ef9e591c002e', {boundingbox:[-4, 6, 10, -6], axis: false, grid: false, keepaspectratio: true}),
2662  *      p = board.create('point', [1, 3]),
2663  *      q = board.create('point', [-2, -4]),
2664  *      l = board.create('line', [p, q]),
2665  *      ineq = board.create('inequality', [l]);
2666  * })();
2667  * </script><pre>
2668  *
2669  * @example
2670  * // Plot the inequality
2671  * //     y >= 2/3 x + 1
2672  * // or
2673  * //     0 >= -3y + 2x +1
2674  * var l = board.create('line', [1, 2, -3]),
2675  *     ineq = board.create('inequality', [l], {inverse:true});
2676  * </pre><div class="jxgbox" id="JXG1ded3812-2da4-4323-abaf-1db4bad1bfbd" style="width: 400px; height: 400px;"></div>
2677  * <script type="text/javascript">
2678  * (function () {
2679  *  var board = JXG.JSXGraph.initBoard('JXG1ded3812-2da4-4323-abaf-1db4bad1bfbd', {boundingbox:[-4, 6, 10, -6], axis: false, grid: false, keepaspectratio: true}),
2680  *      l = board.create('line', [1, 2, -3]),
2681  *      ineq = board.create('inequality', [l], {inverse:true});
2682  * })();
2683  * </script><pre>
2684  *
2685  * @example
2686  * var f = board.create('functiongraph', ['sin(x)', -2*Math.PI, 2*Math.PI]);
2687  *
2688  * var ineq_lower = board.create('inequality', [f]);
2689  * var ineq_greater = board.create('inequality', [f], {inverse: true, fillColor: 'yellow'});
2690  *
2691  *
2692  * </pre><div id="JXGdb68c574-414c-11e8-839a-901b0e1b8723" class="jxgbox" style="width: 300px; height: 300px;"></div>
2693  * <script type="text/javascript">
2694  *     (function() {
2695  *         var board = JXG.JSXGraph.initBoard('JXGdb68c574-414c-11e8-839a-901b0e1b8723',
2696  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2697  *     var f = board.create('functiongraph', ['sin(x)', -2*Math.PI, 2*Math.PI]);
2698  *
2699  *     var ineq_lower = board.create('inequality', [f]);
2700  *     var ineq_greater = board.create('inequality', [f], {inverse: true, fillColor: 'yellow'});
2701  *
2702  *
2703  *     })();
2704  *
2705  * </script><pre>
2706  *
2707  */
2708 JXG.createInequality = function (board, parents, attributes) {
2709     var f, a, attr;
2710 
2711     attr = Type.copyAttributes(attributes, board.options, "inequality");
2712     if (parents[0].elementClass === Const.OBJECT_CLASS_LINE) {
2713         a = board.create("curve", [[], []], attr);
2714         a.hasPoint = function () {
2715             return false;
2716         };
2717 
2718         /**
2719          * @class
2720          * @ignore
2721          */
2722         a.updateDataArray = function () {
2723             var i1,
2724                 i2,
2725                 // This will be the height of the area. We mustn't rely upon the board height because if we pan the view
2726                 // such that the line is not visible anymore, the borders of the area will get visible in some cases.
2727                 h,
2728                 bb = board.getBoundingBox(),
2729                 inverse = Type.evaluate(this.visProp.inverse),
2730                 factor = inverse ? -1 : 1,
2731                 expansion = 1.5,
2732                 w = expansion * Math.max(bb[2] - bb[0], bb[1] - bb[3]),
2733                 // Fake a point (for Math.Geometry.perpendicular)
2734                 // contains centroid of the board
2735                 dp = {
2736                     coords: {
2737                         usrCoords: [1, (bb[0] + bb[2]) * 0.5, inverse ? bb[1] : bb[3]]
2738                     }
2739                 },
2740                 slope1 = parents[0].stdform.slice(1),
2741                 slope2 = slope1;
2742 
2743             // Calculate the area height as
2744             //  expansion times the distance of the line to the
2745             // point in the middle of the top/bottom border.
2746             h =
2747                 expansion *
2748                 Math.max(
2749                     Geometry.perpendicular(parents[0], dp, board)[0].distance(
2750                         Const.COORDS_BY_USER,
2751                         dp.coords
2752                     ),
2753                     w
2754                 );
2755             h *= factor;
2756 
2757             // reuse dp
2758             dp = {
2759                 coords: {
2760                     usrCoords: [1, (bb[0] + bb[2]) * 0.5, (bb[1] + bb[3]) * 0.5]
2761                 }
2762             };
2763 
2764             // If dp is on the line, Geometry.perpendicular will return a point not on the line.
2765             // Since this somewhat odd behavior of Geometry.perpendicular is needed in GEONExT,
2766             // it is circumvented here.
2767             if (
2768                 Math.abs(Mat.innerProduct(dp.coords.usrCoords, parents[0].stdform, 3)) >=
2769                 Mat.eps
2770             ) {
2771                 dp = Geometry.perpendicular(parents[0], dp, board)[0].usrCoords;
2772             } else {
2773                 dp = dp.coords.usrCoords;
2774             }
2775             i1 = [1, dp[1] + slope1[1] * w, dp[2] - slope1[0] * w];
2776             i2 = [1, dp[1] - slope2[1] * w, dp[2] + slope2[0] * w];
2777 
2778             // One of the vectors based in i1 and orthogonal to the parent line has the direction d1 = (slope1, -1)
2779             // We will go from i1 to i1 + h*d1, from there to i2 + h*d2 (with d2 calculated equivalent to d1) and
2780             // end up in i2.
2781             this.dataX = [i1[1], i1[1] + slope1[0] * h, i2[1] + slope2[0] * h, i2[1], i1[1]];
2782             this.dataY = [i1[2], i1[2] + slope1[1] * h, i2[2] + slope2[1] * h, i2[2], i1[2]];
2783         };
2784     } else if (
2785         parents[0].elementClass === Const.OBJECT_CLASS_CURVE &&
2786         parents[0].visProp.curvetype === "functiongraph"
2787     ) {
2788         a = board.create("curve", [[], []], attr);
2789         /**
2790          * @class
2791          * @ignore
2792          */
2793         a.updateDataArray = function () {
2794             var bbox = this.board.getBoundingBox(),
2795                 points = [],
2796                 infty,
2797                 first,
2798                 last,
2799                 len,
2800                 i,
2801                 mi = parents[0].minX(),
2802                 ma = parents[0].maxX(),
2803                 curve_mi,
2804                 curve_ma,
2805                 firstx,
2806                 lastx,
2807                 enlarge = (bbox[1] - bbox[3]) * 0.3, // enlarge the bbox vertically by this amount
2808                 inverse = Type.evaluate(this.visProp.inverse);
2809 
2810             // inverse == true <=> Fill area with y >= f(x)
2811             infty = inverse ? 1 : 3; // we will use either bbox[1] or bbox[3] below
2812 
2813             this.dataX = [];
2814             this.dataY = [];
2815             len = parents[0].points.length;
2816             if (len === 0) {
2817                 return;
2818             }
2819 
2820             bbox[1] += enlarge;
2821             bbox[3] -= enlarge;
2822 
2823             last = -1;
2824             while (last < len - 1) {
2825                 // Find the first point with real coordinates on this curve segment
2826                 for (i = last + 1, first = len; i < len; i++) {
2827                     if (parents[0].points[i].isReal()) {
2828                         first = i;
2829                         break;
2830                     }
2831                 }
2832                 // No real points found -> exit
2833                 if (first >= len) {
2834                     break;
2835                 }
2836 
2837                 // Find the last point with real coordinates on this curve segment
2838                 for (i = first, last = len - 1; i < len - 1; i++) {
2839                     if (!parents[0].points[i + 1].isReal()) {
2840                         last = i;
2841                         break;
2842                     }
2843                 }
2844 
2845                 firstx = parents[0].points[first].usrCoords[1];
2846                 lastx = parents[0].points[last].usrCoords[1];
2847 
2848                 // Restrict the plot interval if the function ends inside of the board
2849                 curve_mi = bbox[0] < mi ? mi : bbox[0];
2850                 curve_ma = bbox[2] > ma ? ma : bbox[2];
2851 
2852                 // Found NaNs
2853                 curve_mi = first === 0 ? curve_mi : Math.max(curve_mi, firstx);
2854                 curve_ma = last === len - 1 ? curve_ma : Math.min(curve_ma, lastx);
2855 
2856                 // First and last relevant x-coordinate of the curve
2857                 curve_mi = first === 0 ? mi : firstx;
2858                 curve_ma = last === len - 1 ? ma : lastx;
2859 
2860                 // Copy the curve points
2861                 points = [];
2862 
2863                 points.push([1, curve_mi, bbox[infty]]);
2864                 points.push([1, curve_mi, parents[0].points[first].usrCoords[2]]);
2865                 for (i = first; i <= last; i++) {
2866                     points.push(parents[0].points[i].usrCoords);
2867                 }
2868                 points.push([1, curve_ma, parents[0].points[last].usrCoords[2]]);
2869                 points.push([1, curve_ma, bbox[infty]]);
2870                 points.push(points[0]);
2871 
2872                 for (i = 0; i < points.length; i++) {
2873                     this.dataX.push(points[i][1]);
2874                     this.dataY.push(points[i][2]);
2875                 }
2876 
2877                 if (last < len - 1) {
2878                     this.dataX.push(NaN);
2879                     this.dataY.push(NaN);
2880                 }
2881             }
2882         };
2883 
2884         // Previous code:
2885         /**
2886          * @class
2887          * @ignore
2888          */
2889         a.hasPoint = function () {
2890             return false;
2891         };
2892     } else {
2893         // Not yet practical?
2894         f = Type.createFunction(parents[0]);
2895         a.addParentsFromJCFunctions([f]);
2896 
2897         if (!Type.exists(f)) {
2898             throw new Error(
2899                 "JSXGraph: Can't create area with the given parents." +
2900                     "\nPossible parent types: [line], [function]"
2901             );
2902         }
2903     }
2904 
2905     a.addParents(parents[0]);
2906     return a;
2907 };
2908 
2909 JXG.registerElement("arrowparallel", JXG.createArrowParallel);
2910 JXG.registerElement("bisector", JXG.createBisector);
2911 JXG.registerElement("bisectorlines", JXG.createAngularBisectorsOfTwoLines);
2912 JXG.registerElement("msector", JXG.createMsector);
2913 JXG.registerElement("circumcircle", JXG.createCircumcircle);
2914 JXG.registerElement("circumcirclemidpoint", JXG.createCircumcenter);
2915 JXG.registerElement("circumcenter", JXG.createCircumcenter);
2916 JXG.registerElement("incenter", JXG.createIncenter);
2917 JXG.registerElement("incircle", JXG.createIncircle);
2918 JXG.registerElement("integral", JXG.createIntegral);
2919 JXG.registerElement("midpoint", JXG.createMidpoint);
2920 JXG.registerElement("mirrorelement", JXG.createMirrorElement);
2921 JXG.registerElement("mirrorpoint", JXG.createMirrorPoint);
2922 JXG.registerElement("orthogonalprojection", JXG.createOrthogonalProjection);
2923 JXG.registerElement("parallel", JXG.createParallel);
2924 JXG.registerElement("parallelpoint", JXG.createParallelPoint);
2925 JXG.registerElement("perpendicular", JXG.createPerpendicular);
2926 JXG.registerElement("perpendicularpoint", JXG.createPerpendicularPoint);
2927 JXG.registerElement("perpendicularsegment", JXG.createPerpendicularSegment);
2928 JXG.registerElement("reflection", JXG.createReflection);
2929 JXG.registerElement("inequality", JXG.createInequality);
2930 
2931 // export default {
2932 //     createArrowParallel: JXG.createArrowParallel,
2933 //     createBisector: JXG.createBisector,
2934 //     createAngularBisectorOfTwoLines: JXG.createAngularBisectorsOfTwoLines,
2935 //     createCircumcircle: JXG.createCircumcircle,
2936 //     createCircumcenter: JXG.createCircumcenter,
2937 //     createIncenter: JXG.createIncenter,
2938 //     createIncircle: JXG.createIncircle,
2939 //     createIntegral: JXG.createIntegral,
2940 //     createMidpoint: JXG.createMidpoint,
2941 //     createMirrorElement: JXG.createMirrorElement,
2942 //     createMirrorPoint: JXG.createMirrorPoint,
2943 //     createNormal: JXG.createNormal,
2944 //     createOrthogonalProjection: JXG.createOrthogonalProjection,
2945 //     createParallel: JXG.createParallel,
2946 //     createParallelPoint: JXG.createParallelPoint,
2947 //     createPerpendicular: JXG.createPerpendicular,
2948 //     createPerpendicularPoint: JXG.createPerpendicularPoint,
2949 //     createPerpendicularSegmen: JXG.createPerpendicularSegment,
2950 //     createReflection: JXG.createReflection,
2951 //     createGrid: JXG.createGrid,
2952 //     createInequality: JXG.createInequality
2953 // };
2954