MathDB
2008 PUMaC Geometry A10/B10

Source:

November 9, 2012
geometrytrigonometry3D geometryspherecombinatorial geometry

Problem Statement

A cuboctahedron is the convex hull of (smallest convex set containing) the 1212 points (±1,±1,0),(±1,0,±1),(0,±1,±1)(\pm 1, \pm 1, 0), (\pm 1, 0, \pm 1), (0, \pm 1, \pm 1). Find the cosine of the solid angle of one of the triangular faces, as viewed from the origin. (Take a figure and consider the set of points on the unit sphere centered on the origin such that the ray from the origin through the point intersects the fi gure. The area of that set is the solid angle of the fi gure as viewed from the origin.)