title: Math constant PI value in C
body: <p>Calculating PI value is one of the complex problem and wikipedia talks about the <a href="http://en.wikipedia.org/wiki/Approximations_of_%CF%80" rel="noreferrer">approximations</a> done for it and says it's difficult to calculate PI accurately. </p>
  
  <p>How does C calculate PI? Does it calculate it every time or is it using a less accurate fixed value?</p>