title: What is start angle and end angle of arc in html5 canvas?
body: <p>I'm learning HTML5 and I"m stuck on arc.</p>
  
  <p>syntax </p>
  
  <pre><code>arc(x, y, radius, startAngle, endAngle, anticlockwise)
  </code></pre>
  
  <p>I'm not getting this startAngle,endAngle perfectly how this two parameters are calculated to
  draw different types of circles,arcs?</p>