THEOREM OF THE DAY: Lambert’s Formula

If $T$ is a triangle in the hyperbolic plane of (negative) Gaussian curvature $K$, with angles $α, β$ and $γ$, then the area of $T$ is given by 

Area of $T = \dfrac{1}{K}(α+β+γ- \dfrac{τ}{2})$

where $τ = 2π$.

Read more »