The swallows can catch the fly
Source:
January 25, 2011
geometry3D geometrytetrahedroncombinatorics unsolvedcombinatorics
Problem Statement
Four swallows are catching a fly. At first, the swallows are at the four vertices of a tetrahedron, and the fly is in its interior. Their maximal speeds are equal. Prove that the swallows can catch the fly.