title: how to use computeArea to calculate the area of a circle?
body: <p>google maps geometry library provides a function:</p>
  
  <p>computeArea(loop:Array.|MVCArray., radius?:number)</p>
  
  <p>which seems can calculate the area of a circle by providing the radius, but no matter how I tried, it didn't seem to work. Any help of how I can use the function? </p>
  
  <p>BTW, fowllowing is a sample of calculating the area of a polygon:</p>
  
  <pre><code>    var nyc = new google.maps.LatLng(40.715, -74.002);
      var london = new google.maps.LatLng(51.506, -0.119);
      var rio = new google.maps.LatLng(-22.916, -43.251);
      var area = google.maps.geometry.spherical.computeArea([nyc, london, rio]);
  </code></pre>