出典:Wikipedia
出典:『Wikipedia』 (2011/07/22 17:48 UTC 版)
In mathematics, the inverse relation of a binary relation is the relation that occurs when you switch the order of the elements in the relation. For example, the inverse of the relation 'child of' is the relation 'parent of'. In formal terms, if
is a relation from X to Y then L − 1 is the relation defined so that
if and only if
(Halmos 1975, p. 40). In another way, 