MathDB

ASU 302 All Soviet Union MO 1980 tetrahedron , cos (AC,BD) <= |CD|/|AB|

Source:

July 19, 2019

trigonometrygeometrytetrahedron3D geometryorthogonal

Problem Statement

The edge

[AC]

of the tetrahedron

ABCD

is orthogonal to

[BC]

, and

[AD]

is orthogonal to

[BD]

. Prove that the cosine of the angle between lines

(AC)

and

(BD)

is less than

|CD|/|AB|