Английская Википедия:Gyroelongated pentagonal birotunda

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In geometry, the gyroelongated pentagonal birotunda is one of the Johnson solids (Шаблон:Math). As the name suggests, it can be constructed by gyroelongating a pentagonal birotunda (either Шаблон:Math or the icosidodecahedron) by inserting a decagonal antiprism between its two halves.

The gyroelongated pentagonal birotunda is one of five Johnson solids which are chiral, meaning that they have a "left-handed" and a "right-handed" form. In the illustration to the right, each pentagonal face on the bottom half of the figure is connected by a path of two triangular faces to a pentagonal face above it and to the left. In the figure of opposite chirality (the mirror image of the illustrated figure), each bottom pentagon would be connected to a pentagonal face above it and to the right. The two chiral forms of Шаблон:Math are not considered different Johnson solids.

Area and Volume

With edge length a, the surface area is

<math>A=\left(10\sqrt{3} + 3\sqrt{25+10\sqrt{5}}\right) a^2\approx37.966236883...a^2,</math>

and the volume is

<math>V=\left(\frac{45}{6}+\frac{17}{6}\sqrt{5} + \frac{5}{6}\sqrt{2\sqrt{650+290\sqrt{5}}-2\sqrt{5}-2}\right) a^3\approx20.584813812...a^3.</math>

See also

• Birotunda

External links

• Шаблон:MathWorld
  • Шаблон:MathWorld