Let $\sin$ be the D164: Standard complex sine function.
Let $\cos$ be the D165: Standard complex cosine function.
Let $z \in \mathbb{C}$ be a D1207: Complex number.
Let $\cos$ be the D165: Standard complex cosine function.
Let $z \in \mathbb{C}$ be a D1207: Complex number.
Then
\begin{equation}
\sin^2 z + \cos^2 z
= 1
\end{equation}