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An octahedron can be any polyhedron with eight faces. In a previous example, the regular octahedron has 6 vertices and 12 edges, the minimum for an octahedron; irregular octahedra may have as many as 12 vertices and 18 edges. [24] There are 257 topologically distinct convex octahedra, excluding mirror images. More specifically there are 2, 11 ...
Plan of the Dome of the Rock, Jerusalem The Tower of the Winds in Athens Octagon buildings and structures are characterized by an octagonal plan form, whether a perfect geometric octagon or a regular eight-sided polygon with approximately equal sides.
The Octagon (Roosevelt Island, New York), once an insane asylum Octagonal buildings and structures are characterized by an octagonal plan form, whether a perfect geometric octagon or a regular eight-sided polygon with approximately equal sides.
Examples include Circoporus octahedrus, Circogonia icosahedra, Lithocubus geometricus and Circorrhegma dodecahedra; the shapes of these creatures are indicated by their names. [5] The outer protein shells of many viruses form regular polyhedra. For example, HIV is enclosed in a regular icosahedron, as is the head of a typical myovirus. [6] [7]
In the 15th-century manuscript De quinque corporibus regularibus by Piero della Francesca, della Francesca already includes a drawing of an octahedron circumscribed around a cube, with eight of the cube edges lying in the octahedron's eight faces. Three octahedra circumscribed in this way around a single cube would form the compound of three ...
It is an example of many classes of polyhedra: Platonic solid, regular polyhedron, parallelohedron, zonohedron, and plesiohedron. The dual polyhedron of a cube is the regular octahedron . The cube is the three-dimensional hypercube , a family of polytopes also including the two-dimensional square and four-dimensional tesseract .
Since it has 8 faces, it is an octahedron. However, the term octahedron is primarily used to refer to the regular octahedron, which has eight triangular faces. Because of the ambiguity of the term octahedron and tilarity of the various eight-sided figures, the term is rarely used without clarification.
It is an example of a Platonic solid and of a deltahedron. The icosahedral graph represents the skeleton of a regular icosahedron. Many polyhedra are constructed from the regular icosahedron. For example, most of the Kepler–Poinsot polyhedron is constructed by faceting. Some of the Johnson solids can be constructed by removing the pentagonal ...