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The regular decagon has Dih 10 symmetry, order 20. There are 3 subgroup dihedral symmetries: Dih 5, Dih 2, and Dih 1, and 4 cyclic group symmetries: Z 10, Z 5, Z 2, and Z 1. These 8 symmetries can be seen in 10 distinct symmetries on the decagon, a larger number because the lines of reflections can either pass through vertices or edges.
A simplicial arrangement formed by 20 lines, the sides and symmetry axes of a regular decagon. Adding the line at infinity produces another simplicial arrangement with 21 lines. An arrangement of lines in the projective plane is said to be simplicial if every cell of the arrangement is bounded by exactly three edges.
The symmetries of this pentagon are linear transformations of the plane as a vector space. If we center the regular polygon at the origin, then elements of the dihedral group act as linear transformations of the plane. This lets us represent elements of D n as matrices, with composition being matrix multiplication.
1-uniform tilings include 3 regular tilings, and 8 semiregular ones, with 2 or more types of regular polygon faces. There are 20 2-uniform tilings, 61 3-uniform tilings, 151 4-uniform tilings, 332 5-uniform tilings and 673 6-uniform tilings. Each can be grouped by the number m of distinct vertex figures, which are also called m-Archimedean tilings.
A non-convex regular polygon is a regular star polygon. The most common example is the pentagram , which has the same vertices as a pentagon , but connects alternating vertices. For an n -sided star polygon, the Schläfli symbol is modified to indicate the density or "starriness" m of the polygon, as { n / m }.
The regular tridecagon has Dih 13 symmetry, order 26. Since 13 is a prime number there is one subgroup with dihedral symmetry: Dih 1, and 2 cyclic group symmetries: Z 13, and Z 1. These 4 symmetries can be seen in 4 distinct symmetries on the tridecagon. John Conway labels these by a letter and group order. [2]
The regular pentadecagon has Dih 15 dihedral symmetry, order 30, represented by 15 lines of reflection. Dih 15 has 3 dihedral subgroups: Dih 5, Dih 3, and Dih 1. And four more cyclic symmetries: Z 15, Z 5, Z 3, and Z 1, with Z n representing π/n radian rotational symmetry. On the pentadecagon, there are 8 distinct symmetries.
The Desargues configuration can be constructed in two dimensions from the points and lines occurring in Desargues's theorem, in three dimensions from five planes in general position, or in four dimensions from the 5-cell, the four-dimensional regular simplex. It has a large group of symmetries, taking any point to any other point and any line ...