Chapter 13, Trigonometric Ratios and Functions - 13.2 Define General Angles and Use Radian Measure - 13.2 Exercises - Skill Practice - Page 863: 20

$\dfrac{5 \pi}{6}$ and $\dfrac{-19\pi}{6}$

a) Need to add $2 \pi$ to the given radian measurements. Thus, we have $\dfrac{-7 \pi}{6}+2 \pi=\dfrac{-7 \pi}{6}+\dfrac{12 \pi}{6}$ $=\dfrac{5\pi}{6}$ b) Need to subtract $2 \pi$ to the given radian measurements. Thus, we have $\dfrac{-7 \pi}{6}-2 \pi=\dfrac{-7 \pi}{6}-\dfrac{12 \pi}{6}$ $=\dfrac{-19\pi}{6}$