Pentagonal orthobirotunda explained

Type:	Birotunda, Johnson
Faces:	2x10 triangles 2+10 pentagons
Edges:	60
Vertices:	30
Properties:	convex
Net:	Johnson_solid_34_net.png

In geometry, the pentagonal orthobirotunda is a polyhedron constructed by attaching two pentagonal rotundae along their decagonal faces, matching like faces. It is an example of Johnson solid.

Construction

The pentagonal orthobirotunda is constructed by attaching two pentagonal rotundas to their base, covering decagon faces. The resulting polyhedron has 32 faces, 30 vertices, and 60 edges. This construction is similar to icosidodecahedron (or pentagonal gyrobirotunda), an Archimedean solid: the difference is one of its rotundas twisted around 36°, making the pentagonal faces connect to the triangular one, a process known as gyration. A convex polyhedron in which all of the faces are regular polygons is the Johnson solid. The pentagonal orthobirotunda is one of them, enumerated as the 34th Johnson solid

J₃₄

Properties

The surface area of an icosidodecahedron

can be determined by calculating the area of all pentagonal faces. The volume of an icosidodecahedron

can be determined by slicing it off into two pentagonal rotunda, after which summing up their volumes. Therefore, its surface area and volume can be formulated as:

\beginA &= \left(5\sqrt+3\sqrt\right) a^2 &\approx 29.306a^2 \\V &= \fraca^3 &\approx 13.836a^3.\end

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pentagonal orthobirotunda".