MathDB
Obtuse triangle on tetrahedron given by plane

Source: Czech and Slovak Olympiad 1990, National Round, Problem 3

October 12, 2024
geometry3D geometrytetrahedronobtuseTriangleplanes

Problem Statement

Let ABCDEFGHABCDEFGH be a cube. Consider a plane whose intersection with the tetrahedron ABDEABDE is a triangle with an obtuse angle φ.\varphi. Determine all φ>π/2\varphi>\pi/2 for which there is such a plane.
Back to ProblemsView on AoPS