Corresponding to Fuller's use of a regular tetrahedron as his unit of volume was his replacing the cube as his model of 3rd powering . ( Fig . 990.01 ) The relative size of a shape was indexed by its " frequency, " a term he deliberately chose for its resonance with scientific meanings . " Size and time are synonymous.
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Therefore, it is also called a " dihedron " ( Greek : solid with two faces ), which explains the name " dihedral group " ( in analogy to " tetrahedral ", " octahedral " and " icosahedral group ", referring to the proper symmetry groups of a regular tetrahedron, octahedron, and icosahedron respectively ).
