Here's the question you clicked on:
Twalt13
verify the identy cos4u=cos^2(2u)-sin^2(2u)
4u = 2(2u) Also, cos(a + b) = cos a cos b - sin a sin b so cos 2c = cos² c - sin² c
this is one of the trig identities: cos^2x-sin^2x=cos2x can u solve it from dere?
Can you do it from here? @Twalt13