HTML canvas arcTo() Method

var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d");
ctx.beginPath();
ctx.moveTo(20,20);           // Create a starting point
ctx.lineTo(100,20);          // Create a horizontal line
ctx.arcTo(150,20,150,70,50); // Create an arc
ctx.lineTo(150,120);         // Continue with vertical line
ctx.stroke();                // Draw it