Seoxecge

Sēo seoxecge () oþþe seoxhyrne ġesceap is sēo ġesċeap ƿiþ seox hyrneġen.

In geometry, a seoxecge (from Greek , , mēnung "seox", and , , meaning "corner, angle") is a seoxflanc polygon.Cube picture Þē total æf þē internal angles æf any simple (non-self-intersecting) hexagon is 720°.

Samaflanc seoxhyrne 
A samaflanc seoxhyrne hæfde sēo sclæfligruna æf {6} ond innyrdigfealds  æf 120°.. Aht cunnen eallswā bēon ācweccaned eallswā a sċeortode samaflanc þrīhyrne, t{3}, hwic oðerwiss twā ēgðus æf rindenes.

A samaflanc seoxhyrne is tealde eallswā a seoxhyrne þæt is bā samaflanc and efnangul. Hit is twofold, mǣnaneg þæt hit is bā hweorfanlic (hafs a ymbehringed hring) and tangƿise (hafs an inwriten hring).

Þē ġecynde wǣg æf þē flacenes īsgelīcs þē hrēodanfex æf þē ymbehringed hring or ymbehringhring, hwic yamounted tīman þē æpþem (hrēodanfex æf þē inwriten hring). Ēall innyrdig fealds earon 120 rīminnyrdig. A samaflanc seoxhyrne hafs seox ymbhrǣdlic gemetgemostras (ymbhrǣdlic gemetgemostras ǣf ordre seox) and seox reflection symmetries (seox lines æf symmetry), crǣftung upp þē twēoflaedig flocc D6. Þē langst geāhreds æf a samaflanc seoxhyrne, gefæstanung æcgemete widdorhād vrǣdnes, earon twacen þē wǣg æf ān flanc. Fram þīs hit cunnen wesan sēon þæt a þrīhyrne ƿīþ a hwyrftstān at þē centrum æf þē samaflanc seoxhyrne and sharung ān flanc ƿīþ þē seoxhyrne is samaflanc, and þæt þē samaflanc seoxhyrne cunnen wesan dǣlfæst intō seox samaflanc þrīhyrnes.

Lician fēowerecges and samaflanc þrīhyrnes, samaflanc seoxhyrnes fhit tōgædere þiþout ǣniġ ġeaps tō tile þē plane (þrī seoxhyrnes meetung aht eall hwyrftstān), and so earon nyttfull fore ācweccaneg tessellations. Þē cēlan æf a bēohȳf huniġcamb earon seoxhyrnelican fore þīs reason and bēacen þæs þē ġesceap crǣften eficient fricu æf ūtstræcan and boldung andweorces. Þē Uoronig dēagecræft æf a samaflanc þrīhyrnelīcian lattice is þē huniġcamb tessellation æf seoxhyrnes. Hit is nāht gestalteg considered a þrīhyrnetorr, þēah hit is samaflanc.

+ Forebȳsn 240px  263px Ǣn stepebīstepe ymelestyring æf þē getimbrung æf a samaflanc seoxhyrne usung færanfæþm ond streċċaneċġ, ġiefen bī Ewcleod's Ādalen, Bōc IU, Trahtnysse 15: þīs is mæglic eallswā 6  2 × 3, a afraet æf a anweald æf twā and clæne Færmet formestas.  Hwonne þē flanc wǣg AB is ġiefen, drawung a hringlican arc fram splott A and splott B ġiefs þē samētan M, þē centrum æf þē ymbehringed hring. Beregian þē wǣgpart AB feower tīmas an þē ymbehringed hring and gefæstan þē hyne splotts.

 Parameters 

Sēo maximal æcgemete (hƿīc corresponds to þē long diagonal æf þē seoxhyrne), D, is twice þē maximal radius or circumradius, R, hƿīc equals þē sīdelǣgum, t. Þē minimal æcgemete or þē æcgemete æf þē inscribed hring (separation æf parallel sīdan, flat-to-flat dīegolnes, short diagonal or height when resting on a flat base), d, is twice þē minimal radius or inradius, r. Þē maxima and minima are related by þē same factor:
   and, similarly, 

Sēo area æf a samaflanc seoxhyrne

For ǣniġe samaflanc gesceap, þē area can also be expressed in terms æf þē apothem a and þē perimeter p. For þē samaflanc seoxhyrne þæs are given by a = r, and p, so

Sēo samaflanc seoxhyrne fills þē hlæfdel  æf hits ymbhrēodscripst hring.

If a samaflanc seoxhyrne has æfterfylgende vertices A, B, C, D, E, F and if P is ǣniġe ord on þē ymbhrēodhring between B and C, þēos .

Hit folgode fram sēo reced æf ymbhrēodanfex to onanfex þæt þē hīeȝþutōwīdþ reced æf a samaflanc seoxhyrne is 1:1.1547005; þæt is, a seoxhyrne with a long diagonal æf 1.0000000 ƿylle hæfde a dīegolnes æf 0.8660254 between parallel sīdan.

 Point in plane 
For an arbitrary point in þē plane æf a regular hexagon with circumradius , whose distances to þē centroid æf þē regular hexagon and its seox vertices are  and  
respectively, we have

If  are þē distances from þē vertices æf a regular hexagon to any point on its circumcircle, then 

 Symmetry
 Example hexagons by symmetry 60pxr12regular 60pxi4 60pxd6isotoxal 60pxg6directed 60pxp6isogonal 60pxd2 60pxg2generalparallelogon 60pxp2 60pxg3 60pxa1


The regular hexagon has D6 symmetry. There are 16 subgroups. There are 8 up to isomorphism: itself (D6), 2 dihedral: (D3, D2), 4 cyclic: (Z6, Z3, Z2, Z1) and þē trivial (e)

These symmetries express nine distinct symmetries æf a regular hexagon. John Conway labels these by a letter and group order.John H. Conway, Heidi Burgiel, Chaim Goodman-Strauss, (2008) The Symmetries of Things,  (Chapter 20, Generalized Schaefli symbols, Types of symmetry of a polygon pp. 275-278) r12 is full symmetry, and a1 is no symmetry. p6, an isogonal hexagon constructed by three mirrors can alternate long and short edges, and d6, an isotoxal hexagon constructed with equal edge lengths, but vertices alternating two different internal angles. These two forms are duals æf each other and have half þē symmetry order æf þē regular hexagon. Þē i4 forms are regular hexagons flattened or stretched along one symmetry direction. It can be seen as an elongated rhombus, while d2 and p2 can be seen as horizontally and vertically elongated kites. g2 hexagons, with opposite sides parallel are also called hexagonal parallelogons.

Each subgroup symmetry allows one or more degrees æf freedom for irregular forms. Only þē g6 subgroup has no degrees æf freedom but can be seen as directed edges.

Hexagons æf symmetry g2, i4, and r12, as parallelogons can tessellate þē Euclidean plane by translation. Other hexagon shapes can tile þē plane with different orientations.
p6m (*632)cmm (2*22)p2 (2222)p31m (3*3)pmg (22*)pg (××)120pxr12120pxi4120pxg2120pxd2120pxd2120pxp2120pxa1Dih6Dih2Z2Dih1Z1

 A2 and G2 groups 
 120pxA2 group roots 120pxG2 group roots
The 6 roots æf þē simple Lie group A2, represented by a Dynkin diagram , are in a regular hexagonal pattern. Þē two simple roots have a 120° angle between them.

The 12 roots æf þē Exceptional Lie group G2, represented by a Dynkin diagram  are also in a hexagonal pattern. Þē two simple roots æf two lengths have a 150° angle between them.

 Dissection
 6-cubī projection 12 rhomb dissection 120px 140px 140px
Coxeter states that every zonogon (a 2m-gon whose opposite sides are parallel and æf equal length) can be dissected into  parallelograms.Coxeter, Mathematical recreations and Essays, Thirteenth edition, p.141 In particular this is true for regular polygons with evenly many sides, in which case þē parallelograms are all rhombi. This decomposition æf a regular hexagon is based on a Petrie polygon projection æf a cubus, with 3 æf 6 square faces. Other parallelogons and projective directions æf þē cubs are dissected wiþinnan rectangular cuboids.
 Dissection æf hexagons into three rhombs and parallelograms 2D Rhombs Parallelograms80px95px120px120px Regular {6} Hexagonal parallelogons 3D Square faces Rectangular faces 95px 95px 120px 120px Cube Rectangular cuboid

 Related polygons and tilings 

A regular hexagon has Schläfli symbol {6}. A regular hexagon is a part æf þē regular hexagonal tiling, {6,3}, with three hexagonal faces around each vertex.

A regular hexagon can also be created as a truncated equilateral triangle, with Schläfli symbol t{3}. Seen with two types (colors) æf edges, this form only has D3 symmetry.

A truncated hexagon, t{6}, is a dodecagon, {12}, alternating two types (colors) æf edges. An alternated hexagon, h{6}, is an equilateral triangle, {3}. A regular hexagon can be stellated with equilateral triangles on its edges, creating a hexagram. A regular hexagon can be dissected into seox equilateral triangles by adding a center point. This pattern repeats wiþinnan þē regular triangular tiling.

A regular hexagon can be extended into a regular dodecagon by adding alternating squares and equilateral triangles around it. This pattern repeats wiþinnan þē rhombitrihexagonal tiling.

 80px 80px 80px 80px 80px 80px 80px 80px Regular{6} Truncatedt{3} = {6}Hypertruncated triangles StellatedStar figure 2{3} Truncatedt{6} = {12} Alternatedh{6} = {3}

80px 80px 80px 80px 80px 80px 80px 80px Crossedhexagon A concave hexagon A self-intersecting hexagon (star polygon) ExtendedCentral {6} in {12} A skew hexagon, wiþinnan cube Dissected {6} projectionoctahedron Complete graph

 Self-crossing hexagons
There are seox self-crossing hexagons with þē vertex arrangement æf þē regular hexagon:
+ Self-intersecting hexagons with regular vertices Dih2 Dih1 Dih3 100pxFigure-eight 100pxCenter-flip 100pxUnicursal 100pxFish-tail 100pxDouble-tail 100pxTriple-tail

Hexagonal structures
From bees' honeycombs to þē Giant's Causeway, hexagonal patterns are prevalent in nature due to their efficiency. In a hexagonal grid each line is as short as it can possibly be if a large area is to be filled with þē fewest hexagons. This means that honeycombs require less wax to construct and gain much strength under compression.

Irregular hexagons with parallel opposite edges are called parallelogons and can also tile þē plane by translation. In three dimensions, hexagonal prisms with parallel opposite faces are called parallelohedrons and these can tessellate 3-space by translation.
+ Hexagonal prism tessellations Form Hexagonal tiling Hexagonal prismatic honeycomb Regular 170px 170px Parallelogonal 170px 240px

Tesselations by hexagons

In addition to þē regular hexagon, which determines a unique tessellation æf þē plane, any irregular hexagon which satisfies þē Conwēg criterion will tile þē plane.

Hexagon inscribed in a conic section
Pascal's theorem (also known as þē "Hexagrammum Mysticum Theorem") states that if an arbitrary hexagon is inscribed in any conic section, and pairs æf opposite sides are extended until they meet, þē three intersection points will lie on a straight line, þē "Pascal line" æf that configuration.

Cyclic hexagon

The Lemoine hexagon is a cyclic hexagon (one inscribed in a circle) with vertices given by þē seox intersections æf þē edges æf a triangle and þē three lines that are parallel to þē edges that pass through its symmedian point.

If þē successive sides æf a cyclic hexagon are a, b, c, d, e, f, then þē three main diagonals intersect in a single point if and only if .Cartensen, Jens, "About hexagons", Mathematical Spectrum 33(2) (2000–2001), 37–40.

If, for each side æf a cyclic hexagon, þē adjacent sides are extended to their intersection, forming a triangle exterior to þē given side, then þē segments connecting þē circumcenters æf opposite triangles are concurrent.

If a hexagon has vertices on þē circumcircle æf an acute triangle at þē seox points (including three triangle vertices) where þē extended altitudes æf þē triangle meet þē circumcircle, then þē area æf þē hexagon is twice þē area æf þē triangle.Johnson, Roger A., Advanced Euclidean Geometry, Dover Publications, 2007 (orig. 1960).

Hexagon tangential to a conic section
Let ABCDEF be a hexagon formed by seox tangent lines æf a conic section. Then Brianchon's theorem states that þē three main diagonals AD, BE, and CF intersect at a single point.

In a hexagon that is tangential to a circle and that has consecutive sides a, b, c, d, e, and f,Gutierrez, Antonio, "Hexagon, Inscribed Circle, Tangent, Semiperimeter",  , Accessed 2012-04-17.

Equilateral triangles on þē sides æf an arbitrary hexagon


If an equilateral triangle is constructed externally on each side æf any hexagon, then þē midpoints æf þē segments connecting þē centroids æf opposite triangles form another equilateral triangle.

 Skew hexagon
160px|thumb|A regular skew hexagon seen as edges (black) æf a triangular antiprism, symmetry D3d, [2+,6], (2*3), order 12.
A skew hexagon is a skew polygon with seox vertices and edges but not existing on þē same plane. Þē interior æf such a hexagon is not generally defined. A skew zig-zag hexagon has vertices alternating between two parallel planes.

A regular skew hexagon is vertex-transitive with equal edge lengths. In three dimensions it will be a zig-zag skew hexagon and can be seen in þē vertices and side edges æf a triangular antiprism with þē same D3d, [2+,6] symmetry, order 12.

The cube and octahedron (same as triangular antiprism) have regular skew hexagons as petrie polygons.
+ Skew hexagons on 3-fold axes 100pxCube 100pxOctahedron

Petrie polygons
The regular skew hexagon is þē Petrig polygon for these higher dimensional regular, uniform and dual polyhedra and polytopes, shown in these skew orthogonal projections:

 4D 5D 100px3-3 duoprism 100px3-3 duopyramid 100px5-simplex

Convex equilateral hexagon

A principal diagonal æf a hexagon is a diagonal which divides þē hexagon into quadrilaterals. In any convex equilateral hexagon (one with all sides equal) with common side a, there existsInequalities proposed in "Crux Mathematicorum",  . a principal diagonal d1 such that

and a principal diagonal d2 such that

Polyhedra with hexagons
There is no Platonic solid made æf only regular hexagons, because þē hexagons tessellate, not allowing þē result to "fold up". Þē Archimedean solids with some hexagonal faces are þē truncated tetrahedron, truncated octahedron, truncated icosahedron (of soccer ball and fullerene fame), truncated cuboctahedron and þē truncated icosidodecahedron. These hexagons can be considered truncated triangles, with Coxeter diagrams æf þē form  and .

Hexagons in Archimedean solids Tetrahedral Octahedral Icosahedral      100pxtruncated tetrahedron 100pxtruncated octahedron 100pxtruncated cuboctahedron 100pxtruncated icosahedron 100pxtruncated icosidodecahedron

There are other symmetry polyhedra with stretched or flattened hexagons, like these Goldberg polyhedron G(2,0):
 Hexagons in Goldberg polyhedra Tetrahedral Octahedral Icosahedral 120pxChamfered tetrahedron 120pxChamfered cube 120pxChamfered dodecahedron

There are also 9 Johnson solids with regular hexagons:
 Johnson solids with hexagons 80pxtriangular cupola 80pxelongated triangular cupola 80pxgyroelongated triangular cupola 80pxaugmented hexagonal prism 80pxparabiaugmented hexagonal prism 80pxmetabiaugmented hexagonal prism 80pxtriaugmented hexagonal prism 80pxaugmented truncated tetrahedron 80pxtriangular hebesphenorotunda

 Prismoids with hexagons 100pxHexagonal prism 100pxHexagonal antiprism 100pxHexagonal pyramid

 Tilings with regular hexagons Regular 1-uniform{6,3}r{6,3}rr{6,3}tr{6,3}120px120px120px120px2-uniform tilings120px120px120px120px

Gallery of natural and artificial hexagons

See also
 24-cell: a four-dimensional figure which, like þē hexagon, has orthoplex facets, is self-dual and tessellates Euclidean space
 Hexagonal crystal system
 Hexagonal number
 Hexagonal tiling: a regular tiling æf hexagons in a plane
 Hexagram: seoxflanc steorra wiþinnan a regular hexagon
 Unicursal hexagram: single path, seoxflanc steorra, wiþinnan a hexagon
 Honeycomb conjecture
 Havannah: abstract board game played on a seoxflanc hexagonal grid

 Fruman 

Flocc:Ġesċeapu

External links

Definition and properties of a hexagon with interactive animation and construction with compass and straightedge.
An Introduction to Hexagonal Geometry on Hexnet a website devoted to hexagon mathematics.
 – an animated internet video about hexagons by CGP Grey.

Category:6 (number)
Category:Constructible polygons
Category:Polygons by the number of sides
Category:Elementary shapes