Hyperbolic polygon area
= Hyperbolic polygon area
For a geodesic hyperbolic $n$-gon of curvature $-1$ with interior angles $\alpha_1,\ldots,\alpha_n$, triangulation or the Gauss--Bonnet theorem gives
$$
\operatorname{area}=(n-2)\pi-\sum_{j=1}^n\alpha_j.
$$