Difference between revisions of "Lituus"
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var b2 = JXG.JSXGraph.initBoard('box2', {axis:true,originX: 250, originY: 250, unitX: 25, unitY: 25}); | var b2 = JXG.JSXGraph.initBoard('box2', {axis:true,originX: 250, originY: 250, unitX: 25, unitY: 25}); | ||
var k = b2.createElement('slider', [[1,8],[5,8],[0,1,4]]); | var k = b2.createElement('slider', [[1,8],[5,8],[0,1,4]]); | ||
| − | var c = b2.createElement('curve', [function(phi){return k.Value()*Math.cos(2.0*phi); }, [0, 0],0, | + | var len = b2.createElement('slider', [[1,7],[5,7],[0,2,2]]); |
| + | var c = b2.createElement('curve', [function(phi){return k.Value()*Math.cos(2.0*phi); }, [0, 0],0, function(){return len.Value()*Math.PI;}], | ||
{curveType:'polar', strokewidth:4}); | {curveType:'polar', strokewidth:4}); | ||
</jsxgraph> | </jsxgraph> | ||
Revision as of 17:09, 18 March 2009
A lituus is a spiral in which the angle is inversely proportional to the square of the radius (as expressed in polar coordinates).
- [math]r^2\theta = k \,[/math]
The JavaScript code to produce this picture
<jsxgraph width="500" height="500" box="box1">
var b1 = JXG.JSXGraph.initBoard('box1', {axis:true,originX: 250, originY: 250, unitX: 25, unitY: 25});
var k = b1.createElement('slider', [[1,8],[5,8],[0,1,4]]);
var c = b1.createElement('curve', [function(phi){return Math.sqrt(k.Value()/phi); }, [0, 0],0, 8*Math.PI],
{curveType:'polar', strokewidth:4});
</jsxgraph>
