Reading Materials:
\[\begin{equation} \sin^2 \theta + \cos^2 \theta = 1 \end{equation}\]
\[\begin{equation} 1 + \tan^2 \theta = \sec^2 \theta \end{equation}\]
\[\begin{equation} 1 + \cot^2 \theta = \csc^2 \theta \end{equation}\]