title: How to define the intersection of three circles?
body: <p>Given three circles with their center point and radius, how can you define the area of intersection?</p>
  
  <p>So far what I have is:</p>
  
  <pre><code>var point1 = {x: -3, y: 0};
  var point2 = {x: 3, y: 0};
  var point3 = {x: 0, y: -3};
  
  var r1 = 5;
  var r2 = 5;
  var r3 = 5;
  
  var area = returnIntersectionArea(point1, point2, point3, r1, r2, r3);
  </code></pre>
  
  <p>Also, if two collide but not the third, the function should return null.
  If none collide, null should be returned.</p>