+32 
ONLY PART C PLEASE
for part c i have tried to convert \(cos^4\Theta \) to \(2cosn\Theta \) which i wrote to be \((2cosn\Theta )^4\) then i can expand it in to the expression of z^n + 1/z^n and the same for sin
however i was told to use this method whist being unsure of why it works, please explain if you can. Thanks
