# Definition:Even Function

## Definition

Let $X \subset \R$ be a symmetric set of real numbers:

$\forall x \in X: -x \in X$

A real function $f: X \to \R$ is an even function if and only if:

$\forall x \in X: \map f {-x} = \map f x$

## Also see

• Results about even functions can be found here.