Science Fair Project Encyclopedia
In geometry, the pentagonal dipyramid is one of the Johnson solids (J13). It is a three-dimensional solid that has equilateral triangles only as faces. It is a deltahedron. It is not a Platonic solid because some vertexes have four faces meeting and others have five faces. However, the solid is face-uniform: for any two faces A and B, there is a rotation of the solid that places face A over face B while leaving the solid occupying the same volume.
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