title: Use X,Y coordinates to plot points inside a circle
body: <p>Is there a way in javascript to plot x,y coordinates so they fall into a circle rather than a square?</p>
  
  <p>For example if I have the following code:</p>
  
  <pre><code>  circleRadius = 100;
    context.drawImage(img_elem, dx, dy, dw, dh);
  </code></pre>
  
  <p>I need to figure out a combination of x,y values that would fall inside a 100 pixel circle. </p>
  
  <p>Thanks!</p>