$$\text { Find all values of } \theta \text {, if } \theta \text { is in the interval } \left[ 0,360 ^ { \circ } \right) \text { and has the given function value. }$$
-$\cos \theta = - \frac { \sqrt { 3 } } { 2 }$
A) $150 ^ { \circ }$ and $210 ^ { \circ }$
B) $210 ^ { \circ }$ and $330 ^ { \circ }$
C) $60 ^ { \circ }$ and $300 ^ { \circ }$
D) $60 ^ { \circ }$ and $120 ^ { \circ }$

Question

Quizplus · Accepted Answer

The cosine function equals $-\frac{\sqrt{3}}{2}$ at $150^\circ$ and $210^\circ$, which are in the second and third quadrants where cosine is negative.

- cos⁡θ=−32\cos \theta = - \frac { \sqrt { 3 } } { 2 }cosθ=−23​​

- $\cos \theta = - \frac { \sqrt { 3 } } { 2 }$