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Schläfli Symbol In geometry, the Schläfli symbol Schläfli symbol is a notation of the form p,q,r,... that defines regular polytopes and tessellations. The Schläfli symbol Schläfli symbol is named after the 19thcen [...More...]  "Schläfli Symbol" on: Wikipedia Yahoo 

Dodecahedron In geometry, a dodecahedron (Greek δωδεκάεδρον, from δώδεκα dōdeka "twelve" + ἕδρα hédra "base", "seat" or "face") is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron, which is a Platonic solid. There are also three regular star dodecahedra, which are constructed as stellations of the convex form. All of these have icosahedral symmetry, order 120. The pyritohedron is an irregular pentagonal dodecahedron, having the same topology as the regular one but pyritohedral symmetry while the tetartoid has tetrahedral symmetry. The rhombic dodecahedron, seen as a limiting case of the pyritohedron, has octahedral symmetry. The elongated dodecahedron and trapezorhombic dodecahedron variations, along with the rhombic dodecahedra, are spacefilling [...More...]  "Dodecahedron" on: Wikipedia Yahoo 

KeplerPoinsot Polyhedra In geometry, a Kepler–Poinsot polyhedron Kepler–Poinsot polyhedron is any of four regular star polyhedra.[1] They may be obtained by stellating the regular convex dodecahedron and icosahedron, and differ from these in having regular pentagrammic faces or vertex figures.Contents1 Characteristics1.1 Nonconvexity 1.2 Euler characteristic Euler characteristic χ 1.3 Duality 1.4 Summary2 Relationships among the regular polyhedra 3 History 4 Regular star polyhedra in art and culture 5 See also 6 References 7 External linksCharacteristics[edit] Nonconvexity[edit] These figures have pentagrams (star pentagons) as faces or vertex figures. The small and great stellated dodecahedron have nonconvex regular pentagram faces [...More...]  "KeplerPoinsot Polyhedra" on: Wikipedia Yahoo 

Hyperbolic Space In mathematics, hyperbolic space is a homogeneous space that has a constant negative curvature, where in this case the curvature is the sectional curvature. It is hyperbolic geometry in more than 2 dimensions, and is distinguished from Euclidean spaces with zero curvature that define the Euclidean geometry, and elliptic geometry that have a constant positive curvature. When embedded to a Euclidean space Euclidean space (of a higher dimension), every point of a hyperbolic space is a saddle point [...More...]  "Hyperbolic Space" on: Wikipedia Yahoo 

Angle Defect In geometry, the (angular) defect (or deficit or deficiency) means the failure of some angles to add up to the expected amount of 360° or 180°, when such angles in the plane would. The opposite notion is the excess. Classically the defect arises in two ways:the defect of a vertex of a polyhedron; the defect of a hyperbolic triangle;and the excess also arises in two ways:the excess of a toroidal polyhedron. the excess of a spherical triangle;In the plane, angles about a point add up to 360°, while interior angles in a triangle add up to 180° (equivalently, exterior angles add up to 360°) [...More...]  "Angle Defect" on: Wikipedia Yahoo 

Reflection Symmetry Reflection symmetry, line symmetry, mirror symmetry, mirrorimage symmetry, is symmetry with respect to reflection. That is, a figure which does not change upon undergoing a reflection has reflectional symmetry. In 2D there is a line/axis of symmetry, in 3D a plane of symmetry. An object or figure which is indistinguishable from its transformed image is called mirror symmetric [...More...]  "Reflection Symmetry" on: Wikipedia Yahoo 

Symmetry Group In group theory, the symmetry group of an object (image, signal, etc.) is the group of all transformations under which the object is invariant with composition as the group operation. For a space with a metric, it is a subgroup of the isometry group of the space concerned. If not stated otherwise, this article considers symmetry groups in Euclidean geometry, but the concept may also be studied in more general contexts as expanded below.Contents1 Introduction 2 One dimension 3 Two dimensions 4 Three dimensions 5 Symmetry Symmetry groups in general 6 See also 7 Further reading 8 External linksIntroduction[edit] The "objects" may be geometric figures, images, and patterns, such as a wallpaper pattern. The definition can be made more precise by specifying what is meant by image or pattern, e.g., a function of position with values in a set of colors. For symmetry of physical objects, one may also want to take their physical composition into account [...More...]  "Symmetry Group" on: Wikipedia Yahoo 

Coxeter Group In mathematics, a Coxeter Coxeter group, named after H. S. M. Coxeter, is an abstract group that admits a formal description in terms of reflections (or kaleidoscopic mirrors). Indeed, the finite Coxeter groups are precisely the finite Euclidean reflection groups; the symmetry groups of regular polyhedra are an example. However, not all Coxeter Coxeter groups are finite, and not all can be described in terms of symmetries and Euclidean reflections [...More...]  "Coxeter Group" on: Wikipedia Yahoo 

Tetrahedral Symmetry A regular tetrahedron has 12 rotational (or orientationpreserving) symmetries, and a symmetry order of 24 including transformations that combine a reflection and a rotation. The group of all symmetries is isomorphic to the group S4, the symmetric group of permutations of four objects, since there is exactly one such symmetry for each permutation of the vertices of the tetrahedron [...More...]  "Tetrahedral Symmetry" on: Wikipedia Yahoo 

Octahedral Symmetry A regular octahedron has 24 rotational (or orientationpreserving) symmetries, and a symmetry order of 48 including transformations that combine a reflection and a rotation [...More...]  "Octahedral Symmetry" on: Wikipedia Yahoo 

Icosahedral Symmetry A regular icosahedron has 60 rotational (or orientationpreserving) symmetries, and a symmetry order of 120 including transformations that combine a reflection and a rotation. A regular dodecahedron has the same set of symmetries, since it is the dual of the icosahedron. The set of orientationpreserving symmetries forms a group referred to as A5 (the alternating group on 5 letters), and the full symmetry group (including reflections) is the product A5 × Z2 [...More...]  "Icosahedral Symmetry" on: Wikipedia Yahoo 

Polyhedron In geometry, a polyhedron (plural polyhedra or polyhedrons) is a solid in three dimensions with flat polygonal faces, straight edges and sharp corners or vertices. The word polyhedron comes from the Classical Greek πολύεδρον, as poly (stem of πολύς, "many") + hedron (form of ἕδρα, "base" or "seat"). A convex polyhedron is the convex hull of finitely many points, not all on the same plane [...More...]  "Polyhedron" on: Wikipedia Yahoo 

Platonic Solid In threedimensional space, a Platonic solid Platonic solid is a regular, convex polyhedron. It is constructed by congruent (identical in shape and size) regular (all angles equal and all sides equal) polygonal faces with the same number of faces meeting at each vertex [...More...]  "Platonic Solid" on: Wikipedia Yahoo 

Angular Defect In geometry, the (angular) defect (or deficit or deficiency) means the failure of some angles to add up to the expected amount of 360° or 180°, when such angles in the plane would. The opposite notion is the excess. Classically the defect arises in two ways:the defect of a vertex of a polyhedron; the defect of a hyperbolic triangle;and the excess also arises in two ways:the excess of a toroidal polyhedron. the excess of a spherical triangle;In the plane, angles about a point add up to 360°, while interior angles in a triangle add up to 180° (equivalently, exterior angles add up to 360°) [...More...]  "Angular Defect" on: Wikipedia Yahoo 

Tessellation A tessellation of a flat surface is the tiling of a plane using one or more geometric shapes, called tiles, with no overlaps and no gaps. In mathematics, tessellations can be generalized to higher dimensions and a variety of geometries. A periodic tiling has a repeating pattern. Some special kinds include regular tilings with regular polygonal tiles all of the same shape, and Semiregular tilings with regular tiles of more than one shape and with every corner identically arranged. The patterns formed by periodic tilings can be categorized into 17 wallpaper groups. A tiling that lacks a repeating pattern is called "nonperiodic". An aperiodic tiling uses a small set of tile shapes that cannot form a repeating pattern. In the geometry of higher dimensions, a spacefilling or honeycomb is also called a tessellation of space. A real physical tessellation is a tiling made of materials such as cemented ceramic squares or hexagons [...More...]  "Tessellation" on: Wikipedia Yahoo 

Euclidean Geometry Euclidean geometry Euclidean geometry is a mathematical system attributed to the Alexandrian Greek mathematician Euclid, which he described in his textbook on geometry: the Elements. Euclid's method consists in assuming a small set of intuitively appealing axioms, and deducing many other propositions (theorems) from these. Although many of Euclid's results had been stated by earlier mathematicians,[1] Euclid was the first to show how these propositions could fit into a comprehensive deductive and logical system.[2] The Elements begins with plane geometry, still taught in secondary school as the first axiomatic system and the first examples of formal proof. It goes on to the solid geometry of three dimensions [...More...]  "Euclidean Geometry" on: Wikipedia Yahoo 