3

Part of 1990 Czech and Slovak Olympiad III A

Problems(1)

Obtuse triangle on tetrahedron given by plane

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

ABCDEFGH

be a cube. Consider a plane whose intersection with the tetrahedron

ABDE

is a triangle with an obtuse angle

\varphi.

\varphi>\pi/2

for which there is such a plane.

geometry3D geometrytetrahedronobtuseTriangleplanes