OK I am confused. I am trying to do a lot of these and they just aren't making sense. I understand what Euler's Identitiy is saying but I don't know how to prove the other things. I am stuck on 50, 53, and 55a. Is there a relationship between cosine and sine I could use for 50. How many terms do I need to multiply together for 53?
--Klosekam 17:03, 12 November 2008 (UTC)
