David Eppstein, at the Geometry Junkyard, has 19 proofs of Euler’s theorem: that for a convex polyhedron, then number of vertices (V), edges (E), and faces (F) satisfies V – E + F = 2.

David Eppstein, at the Geometry Junkyard, has 19 proofs of Euler’s theorem: that for a convex polyhedron, then number of vertices (V), edges (E), and faces (F) satisfies V – E + F = 2.