This is a pentagon, but it could be virtually any regular polygon of any number of sides and of any chosen radius.

pentagon.svg

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" width="300" version="1.1" height="300" baseProfile="tiny" xmlns:xlink="http://www.w3.org/1999/xlink">
  <path id="pentagon"></path>
  <script type="application/ecmascript"><![CDATA[
      var sides = 5,
        radius = 100,
        first = sides % 2 === 0 ? Math.PI / sides : 3 * Math.PI / 2,
        mult = 2 * Math.PI / sides,
        points = ['M'];

      for (var i = 0; i < sides; ++i) {
        points.push(Math.round(radius * Math.cos(first + i * mult) + radius) + ',' + Math.round(radius * Math.sin(first + i * mult) + radius));
      }
      
      points.push('z');
      
      document.getElementById('pentagon').setAttribute('d', points.join(' '));
  ]]></script>
</svg>