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12

Part of 1993 Poland - First Round

Problems(1)

Sum of opposite dihedral angles in a tetrahedron

Source: Poland Math Olympiad 1993 Round 1 #12

6/4/2023
Prove that the sums of the opposite dihedral angles of a tetrahedron are equal if and only if the sums of the opposite edges of this tetrahedron are equal.
geometry3D geometrytetrahedron