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plane _|_ CD , in tetrahedron ABCD

Source: Polish MO Finals 1974 p1

August 23, 2024
geometry3D geometrytetrahedron

Problem Statement

In a tetrahedron ABCDABCD the edges ABAB and CDCD are perpendicular and ∠ACB=∠ADB\angle ACB =\angle ADB. Prove that the plane through ABAB and the midpoint of the edge CDCD, is perpendicular to CDCD.
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