## Precalculus (6th Edition) Blitzer

$\frac{11\pi}{7}$
$\frac{-31\pi}{7}$ add three multiples of $2\pi$ in $\frac{-31\pi}{7}$ to find the positive coterminal angle less than 2$\pi$. $\frac{-31\pi}{7}$ + ($2\pi$ * 3)= $\frac{11\pi}{7}$