Rabbit holes
Da Vinci
Divine proportion
Dodecahedron
Dymaxion
Euclid
Golden mean
Hexagon
Icosahedron
Icosidodecahedron
Making a lamp
Motivation
Octagon
Pentagon
Pacioli
Paper
Plato
Rhombicosido-
decahedron
Rhombicub-
octahedron
Symmetry
Truncation
Wood
Zometool
The icosahedron – 2
Relationship to dodecahedron
The icosahedron has 20 faces, each of which is a regular or equilateral triangle (equal sides and equal interior angles). Each set of five triangles that touch at a tip (vertex) form the outline of a pentagon, so you can also see 12 overlapping pentagons in the icosahedron. This is a visual hint of its relationship to its dual, the dodecahedron.

