Logarithmic spiral: Difference between revisions

From JSXGraph Wiki
No edit summary
No edit summary
Line 15: Line 15:
  var c = board.createElement('curve', [function(phi){return a.Value()*board.pow(Math.E,b.Value()*phi); }, [0, 0], 0, 8*Math.PI],
  var c = board.createElement('curve', [function(phi){return a.Value()*board.pow(Math.E,b.Value()*phi); }, [0, 0], 0, 8*Math.PI],
             {curveType:'polar', strokewidth:4});         
             {curveType:'polar', strokewidth:4});         
  var g = board.createElement('glider', [-2,1,c]);
  var g = board.createElement('glider', [c]);
  var t = board.createElement('tangent', [g], {dash:2,strokeColor:'#a612a9'});
  var t = board.createElement('tangent', [g], {dash:2,strokeColor:'#a612a9'});


Line 33: Line 33:
  var c = board.createElement('curve', [function(phi){return a.Value()*board.pow(Math.E,b.Value()*phi); }, [0, 0],0, 8*Math.PI],
  var c = board.createElement('curve', [function(phi){return a.Value()*board.pow(Math.E,b.Value()*phi); }, [0, 0],0, 8*Math.PI],
             {curveType:'polar', strokewidth:4});         
             {curveType:'polar', strokewidth:4});         
var g = board.createElement('glider', [c]);
var t = board.createElement('tangent', [g], {dash:2,strokeColor:'#a612a9'});
</source>
</source>


[[Category:Examples]]
[[Category:Examples]]
[[Category:Curves]]
[[Category:Curves]]

Revision as of 15:30, 10 March 2009

It can be described in polar coordinates [math]\displaystyle{ (r, \theta) }[/math] by the equation

[math]\displaystyle{ r = ae^{b\theta}\, }[/math]

with real numbers [math]\displaystyle{ a }[/math] and [math]\displaystyle{ b }[/math].

The JavaScript code to produce this picture

<link rel="stylesheet" type="text/css" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css" />
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/prototype.js"></script>
<script type="text/javascript" src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
<div id="jsxgbox" class="jxgbox" style="width:500px; height:500px;"></div>
 board = JXG.JSXGraph.initBoard('jsxgbox', {originX: 250, originY: 250, unitX: 50, unitY: 50});
 var a = board.createElement('slider', [[1,-1],[5,-1],[0,0.3,1]]);
 var b = board.createElement('slider', [[1,-2],[5,-2],[0,0.15,1]]);
 var c = board.createElement('curve', [function(phi){return a.Value()*board.pow(Math.E,b.Value()*phi); }, [0, 0],0, 8*Math.PI],
             {curveType:'polar', strokewidth:4});        
 var g = board.createElement('glider', [c]);
 var t = board.createElement('tangent', [g], {dash:2,strokeColor:'#a612a9'});