QuestionOmar needs to find $\cos \left(-\frac{2 \pi}{3}\right)$. Use the reference angle and quadrant info to solve.

Studdy Solution
Since cosine is negative in the third quadrant, we have $\cos \left(-\frac{2 \pi}{3}\right) = -\cos(60^{\circ}) = -\frac{1}{2}$.
So, Omar should use the reference angle of $60^{\circ}$ and the fact that $-\frac{2 \pi}{3}$ is in the third quadrant to determine $\cos \left(-\frac{2 \pi}{3}\right)=-\frac{1}{2}$.