Chapter 12 - Section 12.6 - Radian Measure - Exercise - Page 417: 6

$2.62\text{ radians}$

To convert degree to radians , multiply $\dfrac{\pi \text{radians}}{180^o}$ to the given degree measurement to obtain: \begin{align*} 150^o \cdot \dfrac{\pi\text{ rad}}{180^o}&=\dfrac{5}{6} \cdot \pi\text{ rad}\\\\ &\approx2.62 \text{ rad}\end{align*}