Question

If cos x = 0.12, which of the following is [–cos(x + 36π)]?

A. 12
B. -12
C. .12
D. -.12

Answer 1

Cosine is periodic with period 2pi. That's why cos(x+2pi*k)=cos x for integer k
Therefore [–cos(x + 36π)]=-cos x=-0.12
Answer D.