Cosine: Difference between revisions
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The cosine is a projection of the complex number exp(−ix) (which is a point on the unit circle in the complex plane) to the real axis on the complex plane. In the following interactive figure, you can drag the point x on the real axis and observe the behaviour of the complex number exp(−ix) and the varying value of cosine(x).   | |||
{|  | |||
|Cosine  | |||
|Unit Circle on the Complex Plane  | |||
|-  | |||
<  | |  <jsxgraph box="boxR" width="500" height="500">   | ||
       var brd1 = JXG.JSXGraph.initBoard('boxR', {boundingbox: [-10, 1.5, 10, -1.5], axis:true});  | |||
       var xr = brd1.create('line',[[-9,0],[9,0]],{visible:false});  | |||
       var x = brd1.create('glider',[-9,0,xr],{visible:true, name:'x'});  | |||
       var y = brd1.create('point',[x.X(),Math.cos(x.X())],{size:1,name:'',strokeColor:'green'});  | |||
       var x1 = brd1.create('segment',[x,y],{visible:true, straightFirst:false,straightLast:false,strokeColor:'red'});  | |||
       x.on('drag', function(){ transform(x);});  | |||
       var f = brd1.create('functiongraph',  | |||
          [function(x){   | |||
	    return Math.cos(x);    | |||
          }]);  | |||
       brd1.create('text',[  | |||
         function(){return x.X()+0.3;},  | |||
         function(){return y.Y()*0.5;},  | |||
         'cos'],{});  | |||
       function transform(x) {  | |||
        p2.setPosition(JXG.COORDS_BY_USER,[Math.cos(x.X()),Math.sin(x.X())]);  | |||
        y.setPosition(JXG.COORDS_BY_USER,[x.X(),Math.cos(x.X())]);  | |||
        brd.update();  | |||
       }  | |||
<  |    </jsxgraph>   | ||
|   <jsxgraph box="box" width="500" height="500">    | |||
       var brd = JXG.JSXGraph.initBoard('box', {boundingbox: [-1.5, 1.5, 1.5, -1.5], axis:true});    | |||
var brd = JXG.JSXGraph.initBoard('box', {boundingbox: [-1.5, 1.5, 1.5, -1.5], axis:true});  |        brd1.addChild(brd);  | ||
       var ax = brd.create('line',[[0,0],[1,0]],{visible:false});  | |||
       var ay = brd.create('line',[[0,0],[0,1]],{visible:false});  | |||
var ax = brd.create('line',[[0,0],[1,0]],{visible:false});  | |||
var ay = brd.create('line',[[0,0],[0,1]],{visible:false});  | |||
var p0 = brd.create('point',[0,0],{fixed:true,visible:false});  |        var p0 = brd.create('point',[0,0],{fixed:true,visible:false});  | ||
var p1 = brd.create('point',[1,0],{name:'',visible:false,fixed:true});  |        var p1 = brd.create('point',[1,0],{name:'',visible:false,fixed:true});  | ||
var c = brd.create('circle',[p0,p1],{dash:2,strokeWidth:1,strokeOpacity:0.6});  |        var c = brd.create('circle',[p0,p1],{dash:2,strokeWidth:1,strokeOpacity:0.6});  | ||
var p2 = brd.create('point',[Math.cos(x.X()),Math.sin(x.X())],{name:'exp(ix)',fixed:true,size:1, strokeColor:'green'});  |        var p2 = brd.create('point',[Math.cos(x.X()),Math.sin(x.X())],{name:'exp(ix)',fixed:true,size:1, strokeColor:'green'});  | ||
var p3 = brd.create('point',[function(){return p2.X();},0.0],{visible:false,name:'',withLabel:false});  |        var p3 = brd.create('point',[function(){return p2.X();},0.0],{visible:false,name:'',withLabel:false});  | ||
var p4 = brd.create('point',[0.0,function(){return p2.Y();}],{visible:false,name:'',withLabel:false});  |        var p4 = brd.create('point',[0.0,function(){return p2.Y();}],{visible:false,name:'',withLabel:false});  | ||
brd.create('line',[p2,p4],{straightFirst:false,straightLast:false,strokeColor:'red'});     // cos  |        brd.create('line',[p2,p4],{straightFirst:false,straightLast:false,strokeColor:'red'});     // cos  | ||
brd.create('text',[  |        brd.create('text',[  | ||
         function(){return (p2.X()+p4.X())*0.3;},  |          function(){return (p2.X()+p4.X())*0.3;},  | ||
         function(){return p2.Y()+0.05;},  |          function(){return p2.Y()+0.05;},  | ||
         'cos'],{});  |          'cos'],{});  | ||
   </jsxgraph>   | |||
|}  | |||
}  | |||
[[Category:Contributions]]  | [[Category:Contributions]]  | ||
[[Category:Examples]]  | |||
[http://www.bookofproofs.org/branches/cosine/ read more about cosine on Bookofproofs]  | |||
Latest revision as of 13:21, 6 March 2016
The cosine is a projection of the complex number exp(−ix) (which is a point on the unit circle in the complex plane) to the real axis on the complex plane. In the following interactive figure, you can drag the point x on the real axis and observe the behaviour of the complex number exp(−ix) and the varying value of cosine(x).
| Cosine | Unit Circle on the Complex Plane |