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In geometry, a heptagon or septagon is a seven-sided polygon or 7-gon.. The heptagon is sometimes referred to as the septagon, using "sept-" (an elision of septua-, a Latin-derived numerical prefix, rather than hepta-, a Greek-derived numerical prefix; both are cognate) together with the Greek suffix "-agon" meaning angle.
{8/2} or 2{4}, like Coxeter diagrams + , can be seen as the 2D equivalent of the 3D compound of cube and octahedron, + , 4D compound of tesseract and 16-cell, + and 5D compound of 5-cube and 5-orthoplex; that is, the compound of a n-cube and cross-polytope in their respective dual positions.
It follows that all vertices are congruent, and the polyhedron has a high degree of reflectional and rotational symmetry. ... 9: 7{4} +2{7} Octagonal prism: 4.4.8:
A regular skew octagon seen as edges of a square antiprism, symmetry D 4d, [2 +,8], (2*4), order 16. A skew octagon is a skew polygon with eight vertices and edges but not existing on the same plane. The interior of such an octagon is not generally defined. A skew zig-zag octagon has vertices alternating between two parallel planes.
There are two regular heptagrams, labeled as {7/2} and {7/3}, with the second number representing the vertex interval step from a regular heptagon, {7/1}. This is the smallest star polygon that can be drawn in two forms, as irreducible fractions. The two heptagrams are sometimes called the heptagram (for {7/2}) and the great heptagram (for {7/3}).
As n approaches infinity, the internal angle approaches 180 degrees. For a regular polygon with 10,000 sides (a myriagon) the internal angle is 179.964°. As the number of sides increases, the internal angle can come very close to 180°, and the shape of the polygon approaches that of a circle. However the polygon can never become a circle.
n = 8, 45°: octad, Octagonal muqarnas, computer-generated (CG), ceiling; C n is the rotation group of a regular n-sided polygon in 2D and of a regular n-sided pyramid in 3D. If there is e.g. rotational symmetry with respect to an angle of 100°, then also with respect to one of 20°, the greatest common divisor of 100° and 360°.
If each edge of an octahedron is replaced by a one-ohm resistor, the resistance between opposite vertices is 1 / 2 ohm, and that between adjacent vertices 5 / 12 ohm. [ 28 ] Six musical notes can be arranged on the vertices of an octahedron in such a way that each edge represents a consonant dyad and each face represents a ...