Question

Which of the following is equal to cos 40° ? A. Sin 30 ° B. Sin 40 ° C. Sin 50 ° D. Sin 60 °

Answer 1

C

Explanation:

using the identity

cos (angle ) = sin( complement ) , that is

cos x = sin (90 - x)

Then

cos40° = sin(90 - 40)° = sin50°