Page 7

The Binary Icosahedron can be described as a semi-
regular solid bound by 12 isosceles facets and 8
equilateral facets.

The isosceles triangles are of a special type--sometimes
called a "Golden Triangle." The apex is 36 degrees
while the base angles are twice that--72 degrees. The
ratio of the base to the sides is .6180339; a proportion
otherwise known as "phi" or "the Golden Section".

The sides of the 8 equilateral triangles are conjoined to
those of the isosceles to complete this solid.

Below: This pattern shows the relationship between
the 12 isosceles triangles. When folded, as shown, the
Binary Icosahedron is formed in three dimensions.

You might notice that the lines defined by the edges of the Binary
Icosahedron are evident in some pentanon spheres. Perhaps the
most apparent example is PS900...compared below.