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 :


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

Also known as
An even function is also seen referred to as a symmetric function.

However, that usage is not recommended on as there are other concepts which bear that name.

Also see

 * Definition:Odd Function