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A pentagon is a 5-sided planar polygon.
Regular pentagons are of particular interest for geometers. On a regular pentagon, the inner angles are equal to $108^\circ$ All ten diagonals have the same length. If $s$ is the length of a side and $d$ is the length of a diagonal, then $$\frac{d}{s}=\frac{1+\sqrt{5}}{2};$$ 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 regular pentahedron 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.
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"pentagon" is owned by rspuzio. [ full author list (2) | owner history (2) ]
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Cross-references: square, edges, opposite, plane, onto, pentahedron, projection, golden number, ratio, side, length, diagonals, angles, inner, regular, polygon, planar
There are 18 references to this entry.
This is version 4 of pentagon, born on 2002-01-05, modified 2007-07-26.
Object id is 1397, canonical name is Pentagon.
Accessed 7967 times total.
Classification:
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Pending Errata and Addenda
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