Coupole (géométrie)En géométrie, une coupole est un solide formé en joignant deux polygones, un (la base) avec deux fois autant d'arêtes que l'autre, par une bande alternée de triangles et de rectangles. Si les triangles sont équilatéraux et les rectangles sont carrés, et que la base et sa face opposée sont des polygones réguliers, alors la coupole est dite « régulière ». Les coupoles hexagonales, octogonales et décagonales sont des solides de Johnson, et peuvent être formées en prenant des sections du cuboctaèdre, du petit rhombicuboctaèdre et du petit rhombicosidodécaèdre, respectivement.
Pavage hexagonal adouciIn geometry, the snub hexagonal tiling (or snub trihexagonal tiling) is a semiregular tiling of the Euclidean plane. There are four triangles and one hexagon on each vertex. It has Schläfli symbol sr{3,6}. The snub tetrahexagonal tiling is a related hyperbolic tiling with Schläfli symbol sr{4,6}. Conway calls it a snub hextille, constructed as a snub operation applied to a hexagonal tiling (hextille). There are three regular and eight semiregular tilings in the plane. This is the only one which does not have a reflection as a symmetry.
Coupole octogonaleIn geometry, the square cupola, sometimes called lesser dome, is one of the Johnson solids (J_4). It can be obtained as a slice of the rhombicuboctahedron. As in all cupolae, the base polygon has twice as many edges and vertices as the top; in this case the base polygon is an octagon. The following formulae for the circumradius, surface area, volume, and height can be used if all faces are regular, with edge length a: The dual of the square cupola has 8 triangular and 4 kite faces: The crossed square cupola is one of the nonconvex Johnson solid isomorphs, being topologically identical to the convex square cupola.
Pavage triangulaire allongéIn geometry, the elongated triangular tiling is a semiregular tiling of the Euclidean plane. There are three triangles and two squares on each vertex. It is named as a triangular tiling elongated by rows of squares, and given Schläfli symbol {3,6}:e. Conway calls it a isosnub quadrille. There are 3 regular and 8 semiregular tilings in the plane. This tiling is similar to the snub square tiling which also has 3 triangles and two squares on a vertex, but in a different order.
Regular skew polyhedronIn geometry, the regular skew polyhedra are generalizations to the set of regular polyhedra which include the possibility of nonplanar faces or vertex figures. Coxeter looked at skew vertex figures which created new 4-dimensional regular polyhedra, and much later Branko Grünbaum looked at regular skew faces. Infinite regular skew polyhedra that span 3-space or higher are called regular skew apeirohedra. According to Coxeter, in 1926 John Flinders Petrie generalized the concept of regular skew polygons (nonplanar polygons) to regular skew polyhedra.
Pavage carré adouciIn geometry, the snub square tiling is a semiregular tiling of the Euclidean plane. There are three triangles and two squares on each vertex. Its Schläfli symbol is s{4,4}. Conway calls it a snub quadrille, constructed by a snub operation applied to a square tiling (quadrille). There are 3 regular and 8 semiregular tilings in the plane. There are two distinct uniform colorings of a snub square tiling. (Naming the colors by indices around a vertex (3.3.4.3.4): 11212, 11213.
Coupole hexagonaleIn geometry, the triangular cupola is one of the Johnson solids (J_3). It can be seen as half a cuboctahedron. The following formulae for the volume (), the surface area () and the height () can be used if all faces are regular, with edge length a: The dual of the triangular cupola has 6 triangular and 3 kite faces: The triangular cupola can be augmented by 3 square pyramids, leaving adjacent coplanar faces. This isn't a Johnson solid because of its coplanar faces.
Tétraèdre équifacialEn géométrie, un tétraèdre équifacial, ou disphénoïde (du grec sphenoeides, « en forme de coin »), est un tétraèdre (non plan) dont les quatre faces sont des triangles isométriques. Une condition équivalente est que les arêtes opposées soient de même longueur. Il a été signalé dans les Annales de Gergonne dès 1810, puis beaucoup étudié par les géomètres des s. Le tétraèdre régulier est équifacial mais un tétraèdre équifacial peut avoir des arêtes de trois longueurs différentes.
