Editing Even and odd functions (section)

===Even functions===
[[Image:Function x^2.svg|right|thumb|<math>f(x)=x^2</math> is an example of an even function.]]
A [[real function]] {{math|''f''}} is '''even''' if, for every {{mvar|x}} in its domain, {{math|−''x''}} is also in its domain and<ref name=FunctionsAndGraphs>{{cite book|first1=I. M.|last1=Gel'Fand|author1-link=Israel Gelfand|first2=E. G.|last2=Glagoleva|author2-link=E. G. Glagoleva|first3=E. E.|last3=Shnol|title=Functions and Graphs|year=1990|publisher=Birkhäuser|isbn=0-8176-3532-7|url-access=registration|url=https://archive.org/details/functionsgraphs0000gelf}}</ref>{{rp|p. 11}}
<math display=block>f(-x) = f(x)</math>
or equivalently
<math display=block>f(x) - f(-x) = 0.</math>

Geometrically, the graph of an even function is [[Symmetry|symmetric]] with respect to the ''y''-axis, meaning that its graph remains unchanged after [[Reflection (mathematics)|reflection]] about the ''y''-axis.

Examples of even functions are:
*The [[absolute value]] <math>x \mapsto |x|,</math>
*<math>x \mapsto x^2,</math>
*<math>x \mapsto x^n</math> for any even integer <math>n,</math>
*[[trigonometric function|cosine]] <math>\cos,</math>
*[[hyperbolic function|hyperbolic cosine]] <math>\cosh,</math>
*[[Gaussian function]] <math>x \mapsto \exp (-x^2). </math>