# Cairo pentagonal tiling

Cairo pentagonal tiling TypeDual semiregular tiling
Facesirregular pentagons
Coxeter diagram          Symmetry groupp4g, [4+,4], (4*2)
p4, [4,4]+, (442)
Rotation groupp4, [4,4]+, (442)
Dual polyhedronSnub square tiling
Face configurationV3.3.4.3.4
Propertiesface-transitive

In geometry, the Cairo pentagonal tiling is a dual semiregular tiling of the Euclidean plane. It is given its name because several streets in Cairo are paved in this design, it is one of 15 known monohedral pentagon tilings. It is also called MacMahon's net after Percy Alexander MacMahon and his 1921 publication New Mathematical Pastimes. Conway calls it a 4-fold pentille.

As a 2-dimensional crystal net, it shares a special feature with the honeycomb net. Both nets are examples of standard realization, the notion introduced by M. Kotani and T. Sunada for general crystal nets.

## Geometry

These are not regular pentagons: their sides are not equal (they have four long ones and one short one in the ratio 1:sqrt(3)-1), and their angles in sequence are 120°, 120°, 90°, 120°, 90°, it is represented by with face configuration V3.3.4.3.4.

It is similar to the prismatic pentagonal tiling with face configuration V3.3.3.4.4, which has its right angles adjacent to each other.

### Variations

The Cairo pentagonal tiling has two lower symmetry forms given as monohedral pentagonal tilings types 4 and 8:

## Dual tiling

It is the dual of the snub square tiling, made of two squares and three equilateral triangles around each vertex. ## Relation to hexagonal tilings

This tiling can be seen as the union of two perpendicular hexagonal tilings, flattened by a ratio of ${\sqrt {3}}$ . Each hexagon is divided into four pentagons; the two hexagons can also be distorted to be concave, leading to concave pentagons. Alternately one of the hexagonal tilings can remain regular, and the second one stretched and flattened by ${\sqrt {3}}$ in each direction, intersecting into 2 forms of pentagons.

## Topologically equivalent tilings

As a dual to the snub square tiling the geometric proportions are fixed for this tiling; however it can be adjusted to other geometric forms with the same topological connectivity and different symmetry. For example, this rectangular tiling is topologically identical.

## Truncated cairo pentagonal tiling

Truncating the 4-valence nodes creates a form related to the Goldberg polyhedra, and can be given the symbol {4+,4}2,1. The pentagons are truncated into heptagons; the dual {4,4+}2,1 has all triangle faces, related to the geodesic polyhedra. It can be seen as a snub square tiling with its squares replaced by 4 triangles.

## Related polyhedra and tilings

The Cairo pentagonal tiling is similar to the prismatic pentagonal tiling with face configuration V3.3.3.4.4, and two 2-uniform dual tilings and 2 3-uniform duals which mix the two types of pentagons. They are drawn here with colored edges, or k-isohedral pentagons.

The Cairo pentagonal tiling is in a sequence of dual snub polyhedra and tilings with face configuration V3.3.4.3.n.

It is in a sequence of dual snub polyhedra and tilings with face configuration V3.3.n.3.n.