Answer
$1$
Work Step by Step
Using figure $13$, $\sin 3.9$ is approximately $-0.7$ (the y-value corresponding to $3.9$ on the circle), $\cos 3.9$ is approximately $-0.7$ (the x-value corresponding to $3.9$ on the circle). Thus approximately $\tan 3.9=\frac{\sin3.9}{\cos 3.9}=\frac{-0.7}{-0.7}=1$
