title: Calculation of trigonometric functions in python
body: <p>How does Python calculate trigonometric functions? 
  I try to calculate using</p>
  
  <pre><code>x = ((0.1-0.001)/2)*math.sin(((1/20)*math.pi*20)+(0.5*math.pi*1))+((0.1-0.001)/2)+0.001
  </code></pre>
  
  <p>I'm getting</p>
  
  <pre><code>x = 0.1
  </code></pre>
  
  <p>why is that? in a usual calculator (radian) i'm getting <code>0.001</code></p>