Difference between revisions of "Range"

 
 
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Let <math>A</math> and <math>B</math> be any sets, and let <math>f:A\to B</math> be any function. Then <math>\{b\in B\mid \mathrm{there\ is\ some\ } a\in A\mathrm{\ such\ that\ } f(a)=b\}</math> is called the '''range''' or '''image''' of <math>f</math>.
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Let <math>A</math> and <math>B</math> be any [[set]]s and let <math>f:A\to B</math> be any [[function]] between them, so that <math>A</math> is the [[domain]] of <math>f</math> and <math>B</math> is the [[codomain]]. Then <math>\{b\in B\mid \mathrm{there\ is\ some\ } a\in A\mathrm{\ such\ that\ } f(a)=b\}</math> is called the '''range''' or '''image''' of <math>f</math>.
  
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Thus, if we have <math>f: \mathbb{R} \to \mathbb{R}</math> given by <math>f(x) = x^2</math>, the range of <math>f</math> is the set of [[nonnegative]] [[real number]]s.
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A function is a [[surjection]] exactly when the range is equal to the codomain.
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== See also ==
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* [[Set notation]]
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[[Category:Definition]]
 
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Latest revision as of 19:15, 3 February 2016

Let $A$ and $B$ be any sets and let $f:A\to B$ be any function between them, so that $A$ is the domain of $f$ and $B$ is the codomain. Then $\{b\in B\mid \mathrm{there\ is\ some\ } a\in A\mathrm{\ such\ that\ } f(a)=b\}$ is called the range or image of $f$.

Thus, if we have $f: \mathbb{R} \to \mathbb{R}$ given by $f(x) = x^2$, the range of $f$ is the set of nonnegative real numbers.

A function is a surjection exactly when the range is equal to the codomain.

See also

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