title: Derivative Calculator
body: <p>I'm interested in building a derivative calculator. I've racked my brains over solving the problem, but I haven't found a right solution at all. May you have a hint how to start? Thanks</p>
  
  <p>I'm sorry! I clearly want to make symbolic differentiation.</p>
  
  <p>Let's say you have the function f(x) = x^3 + 2x^2 + x</p>
  
  <p>I want to display the derivative, in this case f'(x) = 3x^2 + 4x + 1</p>
  
  <p>I'd like to implement it in objective-c for the iPhone.</p>