## Precalculus (10th Edition)

$-0.70\text{ radians}$
Recall that $2\pi\text{rad}=360^\circ$. Hence, $1^\circ=\frac{\pi\text{ radians}}{180^\circ}$. Therefore: $-40^{\circ}=-40 \cdot 1^{\circ}=-40\cdot\frac{\pi\text{ radians}}{180^\circ}\approx-0.70 \text{ radians}$