Question

Verify the identity.

cos (x - y) - cos (x + y) = 2 sin x sin y

Answer 1

I can't really figure out what identities to use

Answer 2

Cos(x - y) = Cos(x)*Cos(y) + Sin(x)*Sin(y)
Cos(x + y) = Cos(x)*Cos(y) - Sin(x)*Sin(y)

Answer 3

ah I see! I figured it out! thank you!

Answer 4

npz