Rounded Corners with arcTo

HTML

<canvas id="myCanvas" width="600" height="400" />

JavaScript

var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');

//Position starting point to draw
ctx.beginPath();     
ctx.moveTo(0,0);

//Top right
ctx.arcTo(0,0,100,100,100);

ctx.stroke();