## Precalculus (6th Edition)

$\approx 2.3$ radians
To approximate the angle whose cosine value is $-0.65$, look up in the given figure the above $x=-0.65$. Notice that the angle that corresponds to $x=-0.65$ is between 2.2 and 2.4 radians. Thus, $\color{blue}{\cos{2.3} \approx -0.65}$