Let $\sin$ be the D1931: Standard real sine function.
Let $\cos$ be the D1927: Standard real cosine function.
The standard real repeating tangent function is the D4364: Real function \begin{equation} \tan : \mathbb{R} \setminus \left\{ \frac{n \pi}{2} : n \in 2 \mathbb{Z} + 1 \right\} \to \mathbb{R}, \quad \tan(x) = \frac{\sin(x)}{\cos(x)} \end{equation}