## Precalculus (6th Edition) Blitzer

$\dfrac{\pi}{4}$
Suppose $\theta = \tan^{-1} (1)$ This gives: $\tan \theta=1$ Now, $\theta = \tan^{-1} (1)=\dfrac{\pi}{4}$ Therefore, $\tan^{-1} (1)=\dfrac{\pi}{4}$