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| | Equivalence relation (Site not responding. Last check: 2007-11-05) |
 | | The relation "has a common factor with" between natural numbers is not an equivalence relation, because although it is reflexive and symmetric, it is not transitive (2 and 6 have a common factor, and 6 and 3 have a common factor, but 2 and 3 do not have a common factor). |
 | | The relation "is the mother of" on the set of all human beings is not and equivalence relation, because although it is reflexive and symmetric, it is not transitive (if A is the mother of B, and B is the mother of C, it does not necessarily mean A is the mother of C) |
 | | In music see octave equivalency, transpositional equivalency, inversional equivalency, enharmonic equivalency, rotationalal equivalency. |
| www.brainyencyclopedia.com /encyclopedia/e/eq/equivalence_relation.html (872 words) |
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