Pentagon equilateral

Figure 2.13. The dodecahedron and the icosahedron are two of the five Platonic solids (regular polyhedra), the others being the tetrahedron, the cube, and the octahedron, (a) The dodecahedron has twelve regular pentagonal faces with three pentagonal faces meeting at a point, (b) The icosahedron has twenty equilateral triangular faces, with five of these meeting at a point.

Each face of a particular solid is the same shape tetrahedra, octahedra and icosa-hedra are composed of equilateral triangles cubes have square faces dodecahedra are composed of regular pentagons. The Archimedean solids are composed of at... 

V A deltahedron is a polyhedron with all faces that arc equilateral triangles. The dcitahedra from n -4 to /t = 12 are tetrahedron (4), trigonal bipyramid (5). octahedron (6). pentagonal bipyramid (7). bisdisphenoid (dodecahedron) (8), tricapped trigonal prism (9). bicapped square aniiprism 110). octadccahedron (II), and icosahedron (12). Most of these arc illustrated in Chapters hand 12. Sec also Fig. 16.50. 

Figure 3.16 A periodic tiling using equilateral (not regular) pentagons (a) and the unit of structure (b) which will tile the area by translation alone. This tiling has been known and used since ancient times...

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