# How do you evaluate tan^-1(cos(pi))?

Hence $\cos \left(\pi\right) = - 1$ we have that
$\theta = {\tan}^{-} 1 \left(- 1\right) \implies \tan \theta = - 1 \implies \theta = {135}^{o} \mathmr{and} \theta = {315}^{o}$