21. The twinned icosahedron is shown in figure 18a. 22. The vertices of a regular icosahedron are those of three mutually orthogonal golden rectangles. 23. The convex hull of two opposite edges of a regular icosahedron forms a golden rectangle. 24. An analogous modification to an octahedron produces an icosahedron , or " snub octahedron ." 25. Another common assembly is a truncated icosahedron . 26. The CeO 12 core defines an icosahedron . 27. The crest's form was inspired by the truncated icosahedron pattern of a football. 28. For example, the tridiminished icosahedron starts with a regular icosahedron with 3 vertices removed. 29. For example, the tridiminished icosahedron starts with a regular icosahedron with 3 vertices removed. 30. 1 ) Icosahedral-An icosahedron is a polygon with 12 vertices and 20 faces.
