title: Math.cos(Math.radians(90)) doesn't give 0
body: <p>The following line of code:</p>
  
  <pre><code>System.out.println( Math.cos( Math.toRadians(90) ) );
  </code></pre>
  
  <p>prints <code>6.123233995736766E-17</code>.</p>
  
  <p>It should print <code>0</code>. What's wrong?</p>