A disk of positive radius \(r\) in the Euclidean plane has area \(\pi r^2\). The same formula holds for a "disk" on the surface of a sphere if the radius is measured chordally in space! If your first thought is That can't be right, you're far from alone.
Handmade in the UK by specialist picture framers using premium fine art paper with a gently textured surface and satin finish, high-quality wood, and an FSC certified off-white mat. Delivered ready for hanging.
