June 3, 2011

« In a more general acceptance of the word, a whole is termed symmetric if it has interchangeable parts. There are many kinds of symmetry; they differ in the number of interchangeable parts, and in the operations which exchange the parts. Thus, a cube has high symmetry; its 6 faces are interchangeable with each other, and so are its 8 vertices, and so are its 12 edges. The expression yz+zx+xy is symmetric; any two of the three letters x, y, z can be interchanged without changing the expression. »
~ “How to solve it”, G. Polya.

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