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In geometry, a Platonic solid is a convex, regular polyhedron in three-dimensional Euclidean space. Being a regular polyhedron means that the faces are congruent (identical in shape and size) regular polygons (all angles congruent and all edges congruent), and the same number of faces meet at each vertex. There are only five such polyhedra:
A polytope is a geometric object with flat sides, which exists in any general number of dimensions. The following list of polygons, polyhedra and polytopes gives the names of various classes of polytopes and lists some specific examples.
For example, a 7-simplex is (1,1) 8 = (1,2,1) 4 = (1,4,6,4,1) 2 = (1,8,28,56,70,56,28,8,1). The number of 1-faces (edges) of the n -simplex is the n -th triangle number , the number of 2-faces of the n -simplex is the ( n − 1) th tetrahedron number , the number of 3-faces of the n -simplex is the ( n − 2) th 5-cell number, and so on.
A regular polyhedron is identified by its Schläfli symbol of the form {n, m}, where n is the number of sides of each face and m the number of faces meeting at each vertex. There are 5 finite convex regular polyhedra (the Platonic solids ), and four regular star polyhedra (the Kepler–Poinsot polyhedra ), making nine regular polyhedra in all.
Shephard originally devised a modified form of Schläfli's notation for regular polytopes. For a polygon bounded by p 1-edges, with a p 2-set as vertex figure and overall symmetry group of order g, we denote the polygon as p 1 (g)p 2. The number of vertices V is then g/p 2 and the number of edges E is g/p 1.
Point 1. Line segment 2. Equilateral triangle (regular trigon) 3. Regular tetrahedron 4. Regular pentachoron or 4-simplex 5. Regular hexateron or 5-simplex... An n-simplex has n+1 vertices. The process of making each simplex can be visualised on a graph: Begin with a point A. Mark point B at a distance r from it, and join to form a line segment.
Nevertheless, there is general agreement that a polyhedron is a solid or surface that can be described by its vertices (corner points), edges (line segments connecting certain pairs of vertices), faces (two-dimensional polygons), and that it sometimes can be said to have a particular three-dimensional interior volume.
In geometry, the Rhombicosidodecahedron is an Archimedean solid, one of thirteen convex isogonal nonprismatic solids constructed of two or more types of regular polygon faces. It has a total of 62 faces: 20 regular triangular faces, 30 square faces, 12 regular pentagonal faces, with 60 vertices , and 120 edges .