Date: 31 December 1980 1511-EST (Wednesday)
From: Guy.Steele at CMU-10A
To: DCP at MIT-MC (David C. Plummer)
Subject:  Icosahedron
CC: cube-lovers at MIT-MC
In-Reply-To:  DCP@MIT-MC's message of 31 Dec 80 11:15-EST
Message-Id: <31Dec80 151120 GS70@CMU-10A>

The icosahedron has twenty faces, not twelve.  It and the
dodecahedron are duals: each has the same number of vertices
as the other has faces.  If you join the centers of the faces
of one with lines, you get the other.  They have the same
number of edges.