Question

Which is equal to sin 36°?
A) sin 54°
B) sin 64°
C) cos 54°
D) cos 64°

Answer 1

The sine of an angle is equal to the cosine of its complement, and the complement of 36° is 90° – 36° = 54°. Therefore, cos 54° is equal to sin 36°.

Answer 2

remember, sin(|x|)=cos(|90-x|)
so sin(|36|)=cos(|90-36|)=cos(|54|)=cos(54)

answer is C