Question

Which of the following are equivalent to the function y = 4cos x - 2? Check all that apply.

A. y = -4cos x + 2
B. y = 4sin(x +π/2 ) - 2
C. y = 4sin(x - π/2) - 2
D. y = 4cos(-x) - 2 ...?

Answer 1

the answer is
D. y = 4cos(-x) - 2
proof
cosine is an even function, it means cos(-x) = cosx
so y = 4cos(-x) - 2 = y = 4cos(x) - 2