Here is my pseudo code:

```
var percentage = 0.781743; // no specific length
var degrees = percentage * 360.0;
var radians = degrees * Math.PI / 180.0;

var x = 50;
var y = 50;
var r = 30;
var s = 1.5 * Math.PI;

var context = canvas.getContext('2d');
context.beginPath();
context.lineWidth = 5;
context.arc(x, y, r, s, radians, false);
context.closePath();
context.stroke();

```

I'm using the [KineticJS](http://www.kineticjs.com/) library to control the shapes I make and redraw them as necessary. My problem is that the above code does not work at all. I assume I have the math incorrect, because if I change `radians` to something like `4.0 * Math.PI` is draws the entire circle.

I've been using [HTML5 Canvas Arc Tutorial](http://www.html5canvastutorials.com/tutorials/html5-canvas-arcs/) for reference.