Conic sections

Ellipse

The input elements for an ellipse are either

• three points: the two foci and a point on the ellipse
• two point and a number: the two foci and the length of the major axis (maybe a function, too).

var brd1=JXG.JSXGraph.initBoard('jxgbox1',{boundingbox:[-3,3,3,-3], keepaspectratio:true});

var A = brd1.create('point',[-1,1]);
var B = brd1.create('point',[1,1]);
var C = brd1.create('point',[0,-1]);
var ell = brd1.create('ellipse',[A,B,C]);

var brd2=JXG.JSXGraph.initBoard('jxgbox2',{boundingbox:[-3,3,3,-3], keepaspectratio:true});

var A = brd2.create('point',[-1,0]);
var B = brd2.create('point',[1,0]);
var s = brd2.create('slider',[[-1,-2],[1,-2],[0,4,10]]);
var ell = brd2.create('ellipse',[A,B,function(){return s.Value();}]);

Hyperbola

The input elements for a hyperbola are either

• three points: the two foci and a point on the hyperbola
• two point and a number: the two foci and the length of the major axis (maybe a function, too).

var brd3=JXG.JSXGraph.initBoard('jxgbox3',{boundingbox:[-3,3,3,-3], keepaspectratio:true});

var A = brd3.create('point',[0,1]);
var B = brd3.create('point',[1,1]);
var C = brd3.create('point',[0,-1]);
var hyp = brd3.create('hyperbola',[A,B,C]);

var brd4=JXG.JSXGraph.initBoard('jxgbox4',{boundingbox:[-3,3,3,-3], keepaspectratio:true});

var A = brd4.create('point',[-1,0]);
var B = brd4.create('point',[1,0]);
var s = brd4.create('slider',[[-1,-2],[1,-2],[0,0.5,3]]);
var hyp = brd4.create('hyperbola',[A,B,function(){return s.Value();}]);

Parabola

The input elements for a parabola are

• a point and a line: focus and the directrix

var brd5=JXG.JSXGraph.initBoard('jxgbox5',{boundingbox:[-3,3,3,-3], keepaspectratio:true});

var A = brd5.create('point',[-1,1]);
var B = brd5.create('point',[1,1]);
var line = brd5.create('line',[A,B]);
var C = brd5.create('point',[0,-1]);
var par = brd5.create('parabola',[C,line]);

Conic section through five points

var brd6=JXG.JSXGraph.initBoard('jxgbox6',{boundingbox:[-3,3,3,-3], keepaspectratio:true});

var A = brd6.create('point',[0.55,0]);
var B = brd6.create('point',[1,1]);
var C = brd6.create('point',[2,-1]);
var D = brd6.create('point',[2,2]);
var E = brd6.create('point',[0.3,-2]);
var con = brd6.create('conic',[A,B,C,D,E]);