Using a double-angle or half-angle formula to simplify the given expressions.

Question

a) if cos^2(25°)-sin^2(25°)=cos(A°), then

A= _____ degrees

b) if cos^2(7x)-sin^2(7x)=cos(B), then

B= _____ .

Answer 1

cos²θ - sin²θ = cos(2θ)

Plug in the given values of θ.