TOT 061 1984 Spring S-O2 S-A2 6 altitudes in tetrahedron. // lines to a plane
Source:
August 19, 2019
geometry3D geometrytetrahedronparallelPlanealtitude
Problem Statement
Six altitudes are constructed from the three vertices of the base of a tetrahedron to the opposite sides of the three lateral faces. Prove that all three straight lines joining two base points of the altitudes in each lateral face are parallel to a certain plane.(IF Sharygin, Moscow)