## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$\pi$
Value of certain composite functions formula: $f(f^{-1}(x)) = \tan{(\tan^{-1}{x})}= x \hspace{25pt} -\infty \leq x \leq \infty$ Thus, $\tan{\left(\tan^{-1}{(\pi)} \right)} = \boxed{\pi}$