I looked for other people that had approximated cos() and sin() and I came across this answer:

[dtb's answer to "Fast Sin/Cos using a pre computed translation array"][1]

Basically he computed that the math.sin() function from the math library was faster than using a look-up table of values. But from what I can tell, this was computed on a PC.

Arduino has a [math library][2] included that can calculate sin() and cos().


  [1]: http://stackoverflow.com/a/2088589/6075112
  [2]: https://www.arduino.cc/en/Reference/MathHeader