Definition:Inverse Cotangent/Real

Definition
Let $x \in \R$ be a real number such that $-1 \le x \le 1$.

The inverse cotangent of $x$ is the multifunction defined as:
 * $\map {\cot^{-1} } x := \set {y \in \R: \map \cot y = x}$

where $\map \cot y$ is the cotangent of $y$.