### Pythagorean and Tangent Identities.

\begin{align*}
\amp \text{Pythagorean identity} \amp\amp \blert{\sin^2 (\theta) + \cos^2 (\theta) = 1}\\
\amp \text{Tangent identity} \amp\amp \blert{\tan (\theta) = \dfrac{\sin (\theta)}{\cos (\theta)}}
\end{align*}