Pentagonal icositetrahedron
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In geometry, a pentagonal icositetrahedron or pentagonal icosikaitetrahedron is a Catalan solid which is the dual of the snub cube. In crystallography it is also called a gyroid.
A geometric construction of the Tribonacci constant (AC), with compass and marked ruler, according to the method described by Xerardo Neira.
Image: Pentagonalicositetrahedronccw
Image: Pentagonalicositetrahedroncw
Pentagon
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In geometry, a pentagon is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°.
Pentagonal cross-section of okra.
Morning glories, like many other flowers, have a pentagonal shape.
Perigone tube of Rafflesia flower.
The gynoecium of an apple contains five carpels, arranged in a five-pointed star