Difference between revisions of "Bijection"
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It has the useful property that for <math>f:X\rightarrow Y</math> that <math>f^{-1}(y)</math> is always defined, and is at most one element. | It has the useful property that for <math>f:X\rightarrow Y</math> that <math>f^{-1}(y)</math> is always defined, and is at most one element. | ||
| − | Thus <math>f^{-1}</math> behaves as a normal function (rather than the always-valid but less useful <math>f^{-1}:Y\rightarrow\mathcal{P}(X)</math> where <math>\mathcal{P}(X)</math> denotes the [[Power | + | Thus <math>f^{-1}</math> behaves as a normal function (rather than the always-valid but less useful <math>f^{-1}:Y\rightarrow\mathcal{P}(X)</math> where <math>\mathcal{P}(X)</math> denotes the [[Power set|power set]] of <math>X</math>) |
{{Definition}} | {{Definition}} | ||
Revision as of 19:09, 27 February 2015
A bijection is a 1:1 map. A map which is both injective and surjective.
It has the useful property that for f:X→Y that f−1(y) is always defined, and is at most one element.
Thus f−1 behaves as a normal function (rather than the always-valid but less useful f−1:Y→P(X) where P(X) denotes the power set of X)
