title: Python cosine function precision
body: <p>From mathematics we know that the cosine of a 90 degree angle is 0 but Python says it's a bit more than that.</p>
  
  <pre><code>import math
  math.cos(math.radians(90))
  6.123233995736766e-17
  </code></pre>
  
  <p>What's the matter between Python and the number "0"?</p>