# Anyone understands how to solve this question?

Nov 30, 2016

See below

#### Explanation:

A product is $0$ only if one of the factors is zero.

$2 \sin x - 1 = 0$ only if $\sin x = - \frac{1}{2}$.

On $\left[0 , 2 \pi\right\}$, the numbers with sine equal to $- \frac{1}{2}$ are $\frac{7 \pi}{6}$ and $\frac{11 \pi}{6}$

$\cos x = 0$ at $\frac{\pi}{2}$ and at $\frac{3 \pi}{2}$