Soviet Union 13
Source: IMO LongList 1959-1966 Problem 56
September 2, 2004
geometry3D geometrytetrahedroncircumcirclesphereIMO ShortlistIMO Longlist
Problem Statement
In a tetrahedron, all three pairs of opposite (skew) edges are mutually perpendicular. Prove that the midpoints of the six edges of the tetrahedron lie on one sphere.