\displaystyle[br]\begin{equation*} \frac{\frac{2}{\tan \theta}}{\frac{1}{\tan^2 \theta} - 1} = \cdots = \frac{2 \tan \theta}{1 - \tan^2 \theta}\end{equation*}
\displaystyle[br]\begin{equation*} \frac{\frac{2}{\tan \theta}}{\frac{1}{\tan^2 \theta} - 1} = \cdots = \frac{2 \tan \theta}{1 - \tan^2 \theta}\end{equation*}