I've always had problems with these. Surely it cant be that hard, but I really cant get my head around them as it stands, even if it is just proving them - Maybe because I cant find many practical uses for it.. Anyway, these are the following coursework questions due for tomorrow. Would be very greatful if you could provide full answers so I can actually start to understand these damned things. Cheers!

[Y=Theta]

12) Using double angle formulae rewrite in terms of and (Raised to any power).

13) Prove the following identitys:

a)

b)

c)

For c) we were told to go about doing the right hand side first.

Thanks again!