Polar curve plotter

function r(t) {return 0.2*t; };

The JavaScript code

<source lang="javascript"> board = JXG.JSXGraph.initBoard('jxgbox', {axis:true, boundingbox:[-5,5,5,-5]}); a = board.createElement('slider', [[0,-1],[3,-1],[-4*Math.PI,0,0]], {style:6, name:'a'}); b = board.createElement('slider', [[0,-2],[3,-2],[0,7,4*Math.PI]], {style:6, name:'b'}); function plot(){

 eval(document.getElementById("eingabe").value);
 graph = board.createElement('curve', [
           x,y, 
           function(){return a.Value();}, 
           function(){return b.Value();}
           ], 
           {strokeColor:'red', strokeWidth:2}
         );
 board.update();

}

function clearAll() {

 JXG.JSXGraph.freeBoard(board);
 board = JXG.JSXGraph.initBoard('jxgbox', {axis:true, originX: 250, originY: 250, unitX: 50, unitY: 50});
 a = board.createElement('slider', [[0,-1],[3,-1],[-4*Math.PI,0,0]], {style:6, name:'a'});
 b = board.createElement('slider', [[0,-2],[3,-2],[0,7,4*Math.PI]], {style:6, name:'b'});

}

plot(); <source>