function drawShape(){
        // get the canvas element using the DOM
        var canvas = document.getElementById('tutorial');

        // Make sure we don't execute when canvas isn't supported
        if (canvas.getContext){

          // use getContext to use the canvas for drawing
          var ctx = canvas.getContext('2d');
          var sideA = 30;
          var angleB = 0.57;
          var sideC = 60;
          var x = 25;
          var y = 25;
          
          // Outline triangle
          ctx.beginPath();
          ctx.moveTo(x,y);
          ctx.lineTo(x+sideC,y);
          ctx.rotate(angleB);
          ctx.lineTo(x+sideC+sideA,y);
          ctx.rotate(-angleB);
          ctx.lineTo(x,y);
          ctx.stroke();
          
          
        } else {
          alert('You need Safari or Firefox 1.5+ to see this demo.');
        }
      }

drawShape();

<html>
  <head>
    <title>A canvas lineTo example</title>
    <meta name="DC.creator" content="Kamiel Martinet, http://www.martinet.nl/">
    <meta name="DC.publisher" content="Mozilla Developer Center, http://developer.mozilla.org">

    <style type="text/css">
      body { margin: 20px; font-family: arial,verdana,helvetica; background: #fff;}
      h1 { font-size: 140%; font-weight:normal; color: #036; border-bottom: 1px solid #ccc; }
      canvas { border: 2px solid #000; float: left; margin-right: 20px; margin-bottom: 20px; }
      pre { float:left; display:block; background: rgb(238,238,238); border: 1px dashed #666; padding: 15px 20px; margin: 0 0 10px 0; }
    </style>
  </head>

  <body onload="drawShape();">
    <h1>A canvas <code>moveto</code> example</h1>
    <div>
      <canvas id="tutorial" width="150" height="150"></canvas>
      <pre>
function drawShape(){
  // get the canvas element using the DOM
  var canvas = document.getElementById('tutorial');

  // Make sure we don't execute when canvas isn't supported
  if (canvas.getContext){

    // use getContext to use the canvas for drawing
    var ctx = canvas.getContext('2d');

    // Filled triangle
    ctx.beginPath();
    ctx.moveTo(25,25);
    ctx.lineTo(105,25);
    ctx.lineTo(25,105);
    ctx.fill();
    
    // Stroked triangle
    ctx.beginPath();
    ctx.moveTo(125,125);
    ctx.lineTo(125,45);
    ctx.lineTo(45,125);
    ctx.closePath();
    ctx.stroke();

  } else {
    alert('You need Safari or Firefox 1.5+ to see this demo.');
  }
}
      </pre>
    </div>
  </body>

</html>

jsFiddle