title: Why html5 canvas tag uses PI value to draw circle?
body: <pre><code>var c = document.getElementById("myCanvas");
  var cir = c.getContext("2d");
  cir.beginPath();
  cir.arc(100, 100, 50, 0, 2* Math.PI );
  cir.stroke();
  </code></pre>
  
  <p>or </p>
  
  <pre><code>var c = document.getElementById("myCanvas");
  var cir = c.getContext("2d");
  cir.beginPath();
  cir.arc(100, 100, 50, 0, 6.14);
  cir.stroke();
  </code></pre>
  
  <p>This two code can draw a full circle so in this why we are using pi value in this ?</p>