## Precalculus (6th Edition) Blitzer

(-$\frac{\sqrt 3}{2}$ , -$\frac{1}{2}$) csc $\frac{7\pi}{6}$ is computed by $\frac{1}{y}$. So csc $\frac{7\pi}{6}$ = $\frac{1}{-\frac{1}{2}}$ = -2.