In a regular tetrahedron

MATHEMATICS · Single correct · IB Diploma Programme · Mathematics: Analysis and Approaches · Geometry and Trigonometry · Geometry and Trigonometry

Problem

In a regular tetrahedron, let

\theta

be angle between any edge and a face not containing the edge. The value of

\cos^2 \theta

is (1) 1/6 (2) 1/9 (3) 1/3 (4) None of these