Lituus: Difference between revisions
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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', | var c = b2.createElement('curve', | ||
[function(t){ return b2.I([0,t],function(u){return Math.sin(u)*Math.sin(u);}); }, | [function(t){ return k.Value()*b2.I([0,t],function(u){return Math.sin(u)*Math.sin(u);}); }, | ||
function(t){ return b2.I([0,t],function(u){return Math.cos(u)*Math.cos(u);}); }, | function(t){ return k.Value()*b2.I([0,t],function(u){return Math.cos(u)*Math.cos(u);}); }, | ||
0, 8*Math.PI], | 0, 8*Math.PI], | ||
{strokewidth:4}); | {strokewidth:4}); | ||
Revision as of 08:18, 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]\displaystyle{ 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>
