Because, and this is just a hunch, I don't believe that you would accept anything that I showed you.
Rubbish! Being able to prove something is the only way to get credability. Show me some code that proves that calculating sin/cos is faster than using lookup tables and I'll take back what I said. I already ran Wolron's example and the lookup tables are still loads faster.
Just because someone decides to argue their point, doesn't mean that they don't know what they are talking about - in fact this community has a large number of very knowledgable people.
But how can someone argue their point without producing evidence? This is one of the biggest problems in this forum. Some people are making comments and even giving the wrong advice to others without providing a single shread of evidence to back up their argument.
Anyway, I have provided evidence to the original starter of this thread that lookup tables are faster. I am happy in the knowledge that this person has been given the correct advice by me and not some 'Now it all amateur' who gives the impression he knows his stuff without providing evidence.