IMO LongList 1967, Poland 2
Source: IMO LongList 1967, Poland 2
December 16, 2004
geometry3D geometryspheretetrahedroncircumcircleIMO ShortlistIMO Longlist
Problem Statement
Prove this proposition: Center the sphere circumscribed around a tetrahedron which coincides with the center of a sphere inscribed in that tetrahedron if and only if the skew edges of the tetrahedron are equal.