title: Why does Math.cos(90 * Math.PI/180) yield 6.123031769111... and not zero?
body: <p>I convert degrees to radians (degrees * Math.PI/180) but why does the following:</p>
  
  <pre><code>Math.cos(90 * Math.PI/180)
  </code></pre>
  
  <p>yield 6.123031769111... and not zero?</p>
  
  <p>I'm trying to perform 2D rotations uses matrixes and the results are completely out of whack.</p>