midpoints of the six edges of a tetrahedron lie on a sphere
Source: Germany Federal - Bundeswettbewerb Mathematik 1990, round 1, p4
February 21, 2020
spheremidpoints3D geometrytetrahedrongeometry
Problem Statement
Suppose that every two opposite edges of a tetrahedron are orthogonal. Show that the midpoints of the six edges lie on a sphere.