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Prove consphericity in a tetrahedron

Source: Croatian MO 2004 3rd Grade P3

April 9, 2021
geometry3D geometrytetrahedron

Problem Statement

The altitudes of a tetrahedron meet at a single point. Prove that this point, the centroid of one face of the tetrahedron, the foot of the altitude on that face, and the three points dividing the other three altitudes in ratio 2:12:1 (closer to the feet) all lie on a sphere.