Problem: If \displaystyle y= \tan\left(x+\pi \right), find x as a function of y.
Solution:
\begin{align*}
y & = \tan\left(x+\pi \right) \\
x+\pi & = \tan^{-1}y \\
x & = \tan^{-1}y-\pi \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\
\end{align*}