# Equidecomposability of pentagonal antiprism and metabidinimished icosahedron

Izidor Hafner

Faculty of Electrical Engineering, University of Ljubljana

Trzaska 25, 1000 Ljubljana, Slovenia

e-mail: izidor.hafner@fe.uni-lj.si

If a pentagonal pyramid (Johnson solid 2) is cut off the icosahedron , we get the
gyroelongated pentagonal pyramid (Johnson solid 2: J2). If we cut off another pentagonal pyramid, we get
either a pentagonal antiprism or a metabidinimished icosahedron (J62). If we cut three pentagonal pyramids,
we get a tridiminished icosahedron (J63).Click on the picture to activate Live3D graphics [3].

It is obvious, that the pentagonal antiprism and the metabidinimished icosahedron have the same volume.
But they have the same complement relative to the rhombic triacontahedron, namely the complement consists of
2 pentagonal cups and 10 triangular pyramids. This means they are equidecomposable [1].

To make a paper model use the following nets:

References

[1] V.G. Boltjanskii, Tretja problema Hilberta, Nauka, Moskva 1977.

[2] I. Hafner, Live3D Animation to Solution of Conway-Radin-Sadun problem, Visual Mathematics, Volume 9, No. 1, 2007 ,1

[3] Martin Kraus' Live3D applet http://www.vis.uni-stuttgart.de/~kraus/index.html