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

C. I don't know how to tell you to do it. But hopefully your teacher will allow you to use a calculator. If so you know that sin 36 can not = the same as sin 54 or sin 64 so you can rule those out automatically. That will leave you with cos so try in your calculator cos 54 and cos 64 usually which ever is the closest number to the number you start out with will be your answer. Hope this helped some.