title: Value of sine 180 is coming out as 1.22465e-16
body: <p>I want to implement a Sine and Cosine calculator in ios4:</p>
  
  <pre><code>if([operation isEqual:@"sin"]){
      operand = (operand*M_PI/180.0);
      operand=sin(operand);
  }
  </code></pre>
  
  <p>The code gives me correct answer for values from 0 through 90.</p>
  
  <p>When I give value of 180, I get <code>1.22465e-16</code> as an answer.  I expect zero.</p>
  
  <p>Where does this small difference come from?</p>