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The regular icosahedron can also be constructed starting from a regular octahedron. All triangular faces of a regular octahedron are breaking, twisting at a certain angle, and filling up with other equilateral triangles. This process is known as snub, and the regular icosahedron is also known as snub octahedron. [5]
The convex regular icosahedron is usually referred to simply as the regular icosahedron, one of the five regular Platonic solids, and is represented by its Schläfli symbol {3, 5}, containing 20 triangular faces, with 5 faces meeting around each vertex. Its dual polyhedron is the regular dodecahedron {5, 3} having three regular pentagonal faces ...
The regular polyhedra show this duality as follows: The tetrahedron is self-dual, i.e. it pairs with itself. The cube and octahedron are dual to each other. The icosahedron and dodecahedron are dual to each other. The small stellated dodecahedron and great dodecahedron are dual to each other.
Three members of the set can be deltahedra, that is, constructed entirely of equilateral triangles: the gyroelongated square bipyramid, a Johnson solid; the icosahedron, a Platonic solid; and the gyroelongated triangular bipyramid if it is made with equilateral triangles, but because it has coplanar faces is not strictly convex.
Icosahedral symmetry fundamental domains A soccer ball, a common example of a spherical truncated icosahedron, has full icosahedral symmetry. Rotations and reflections form the symmetry group of a great icosahedron. In mathematics, and especially in geometry, an object has icosahedral symmetry if it has the same symmetries as a regular icosahedron.
Category:Platonic solids for the five convex regular polyhedra. Category:Kepler–Poinsot polyhedra for the four non-convex regular polyhedra. Category:Archimedean solids for the remaining convex semi-regular polyhedra, excluding prisms and antiprisms. Category:Quasiregular polyhedra for uniform polyhedra which are also edge-transitive.
The other two Kepler–Poinsot polyhedra (the great stellated dodecahedron and great icosahedron) do not have regular hyperbolic tiling analogues. If m is even, depending on how we choose to define {m/2}, we can either obtain degenerate double covers of other tilings or compound tilings.
The face-transitive polyhedra comprise a set of 9 regular polyhedra, two finite sets comprising 66 non-regular polyhedra, and two infinite sets: 5 regular convex Platonic solids: regular tetrahedron, cube, regular octahedron, regular dodecahedron, and regular icosahedron. The regular octahedron is dual to the cube, and the regular icosahedron ...