Icosahedron is one of only five Platonic solids. This is a regular polyhedron with 12 vertices, 30 edges, and 20 faces. All faces are regular triangles and at every vertex meet five faces and five edges.
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Drag the mouse to rotate the icosahedron. Use the right button to remove and put back individual faces.
(Acknowledgement: I have learned most of Java details from the implementation by Meiko Rachimow.)
The word icosahedron originates with the Greek eikosi (20). The other Platonic solids are tetrahedron, octahedron, dodecahedron, cube. With 20 faces, 30 edges, and 12 vertices a dodecahedron confirms to the Euler's theorem:
Copyright © 1996-2017 Alexander Bogomolny