pentagon


A pentagonMathworldPlanetmath is a 5-sided planar polygon.

Regular pentagons are of particular interest for geometers. On a regular pentagon, the inner angles are equal to 108. All ten diagonals have the same length. If s is the length of a side and d is the length of a diagonal, then

ds=1+52;

that is, the ratio between a diagonal and a side is the Golden Number.

A regular pentagon (along with its diagonals) can also be obtained as the projection of a regularPlanetmathPlanetmathPlanetmath pentahedronMathworldPlanetmath in four dimensional space onto a plane determined by two opposite edges. This is analogous to the way a square with its diagonals can be obtained as the projection of a tetrahedrononto a plane determined by two opposite edges.

Title pentagon
Canonical name Pentagon
Date of creation 2013-03-22 12:10:19
Last modified on 2013-03-22 12:10:19
Owner rspuzio (6075)
Last modified by rspuzio (6075)
Numerical id 8
Author rspuzio (6075)
Entry type Definition
Classification msc 51-00
Related topic Triangle
Related topic PolygonMathworldPlanetmathPlanetmath
Related topic HexagonMathworldPlanetmath
Related topic RegularDecagonInscribedInCircle