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.
Printed on archival quality Hahnemühle German etching paper (310gsm) with a velvety surface.
