Question

how to use the sum or difference identity to prove
cos (x- pi/2)= sinx

I don't remember how to do it

please helps

Answer 1

\[\cos(A - B) = \cos(A)\cos(B) + \sin(A)\sin(B)\]

Answer 2

Here, A = x and B = pi/2

Answer 3

Just use it and tell me where you have arrived by using this..

Answer 4

will do

Answer 5

I got the answer. I thought I had to use the co function identities, that's why I was confused how to do it. The identity you used I was told is called the compound angle identity . Thank you