Untitled

<!DOCTYPE html>
<html>
<head><title>Canvas code example</title>
<script type="text/javascript">

function Uaktualnij() {
 //var a1= document.getElementById('a1').value;
 //var a2= document.getElementById('a2').value;
 //var b1= document.getElementById('b1').value;
 //var b2= document.getElementById('b2').value;
  var a1=1;
  var a2=1;
  var b1=1;
  var b2=1;
}

function fun1(x) {return a1 * Math.sin(b1 * x);  }
function fun2(x) {return a2 * Math.cos(b2 * x);}

function draw() {
 var canvas = document.getElementById("canvas");
 if (null==canvas || !canvas.getContext) return;

 var axes={}, ctx=canvas.getContext("2d");
 axes.x0 = .5 + .5*canvas.width;  // x0 pixels from left to x=0
 axes.y0 = .5 + .5*canvas.height; // y0 pixels from top to y=0
 axes.scale = 40;                 // 40 pixels from x=0 to x=1
 axes.doNegativeX = true;

 showAxes(ctx,axes);
 funGraph(ctx,axes,fun1,"rgb(11,153,11)",1);
 funGraph(ctx,axes,fun2,"rgb(66,44,255)",2);
}

function funGraph (ctx,axes,func,color,thick) {
 var xx, yy, dx=4, x0=axes.x0, y0=axes.y0, scale=axes.scale;
 var iMax = Math.round((ctx.canvas.width-x0)/dx);
 var iMin = axes.doNegativeX ? Math.round(-x0/dx) : 0;
 ctx.beginPath();
 ctx.lineWidth = thick;
 ctx.strokeStyle = color;

 for (var i=iMin;i<=iMax;i++) {
  xx = dx*i; yy = scale*func(xx/scale);
  if (i==iMin) ctx.moveTo(x0+xx,y0-yy);
  else         ctx.lineTo(x0+xx,y0-yy);
 }
 ctx.stroke();
}

function showAxes(ctx,axes) {
 var x0=axes.x0, w=ctx.canvas.width;
 var y0=axes.y0, h=ctx.canvas.height;
 var xmin = axes.doNegativeX ? 0 : x0;
 ctx.beginPath();
 ctx.strokeStyle = "rgb(128,128,128)";
 ctx.moveTo(xmin,y0); ctx.lineTo(w,y0);  // X axis
 ctx.moveTo(x0,0);    ctx.lineTo(x0,h);  // Y axis
 ctx.stroke();
}
</script>
</head>
<body>

<form id="searchform" method="get" name="searchform">
			<input type="number" id="a1" name="a1" />
			<input type="number" id="a2" name="a2" />
			<input type="number" id="b1" name="b1" />
			<input type="number" id="b2" name="b2" />
			<input type="submit" id="searchbutton" onclick="Uaktualnij();" value="yes" />
			</form>
<button onclick="Uaktualnij()">Update</button>
<button onclick="draw()">Click</button>
<canvas id="canvas" width="502" height="108"></canvas>
</body>
</html>