I don't understand,please be clear!
Prove that each equation is an identity.
I tried to do the problems, but I am stuck.
1. cos^4 t-sin^4 t=1-2sin^2 t
2. 1/cos s= csc^2 s - csc s cot s
3. (cos x/ sec x -1)- (cos x/ tan^2x)=cot^2 x
4. sin^3 z cos^2 z= sin^3 z - sin^5 z