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| | Group Theory book |
 | | It is kind of fun to decompose, for each n, the group of units of Z(n), into a direct sum of cyclic groups. |
 | | the first interesting ones are "dihedral" groups, (symmetries of a polygon), then the platonic solid groups, symmetries of the cube, tetrahedron, and (the first really interesting one) the "icosahedral group", symmetries of the icosahedron, of order 60, and isomorphic to the alternating group A(5). |
 | | Of course one should be aware of the symmetric groups S(n), of all permutations of a set of n elements, in which A(n) is the unique normal subgroup of index 2. |
| www.physicsforums.com /showthread.php?p=920330 (1133 words) |
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