Prove Pythagoras' Theorem for right-angled spherical triangles.
An account of how axioms underpin geometry and how by changing one
axiom we get an entirely different geometry.
How do we measure curvature? Find out about curvature on soccer and rugby balls and on surfaces of negative curvature like banana skins.
This article outlines the underlying axioms of spherical geometry giving a simple proof that the sum of the angles of a triangle on the surface of a unit sphere is equal to pi plus the area of the. . . .