Question

Which of the following expressions is equal to sin⁡(-150°)?

A. sin(30°)
B. -sin(-30°)
C. -sin(30°)
D. sin(150°)

Answer 1

C. -sin(30°)

Explanation:

180-150=30

-sin(30) = -.5 on calculator j like sin(-150) is

Answer 2

Check the picture below.

let's notice that the angle -150° has a reference angle of 30°, so any trigonometric function for either angle will be the same value, however, let's recall that the sine or y-coordinate is negative on the III Quadrant, so sin(-150°) is the same as sin(30°) BUT negative, -sin(30°).