Question

Cos (A − B)

Answer 1

Answer is choice C) cosine is even; sine is odd

The properties that come with even and odd functions are...
f(-x) = f(x) indicates we have an even function. So cos(-x) = cos(x)
f(-x) = -f(x) indicates we have an odd function. So sin(-x) = -sin(x)

note: the end result of the proof will lead to cos(A)cos(B)+sin(A)sin(B)