# Even function

An even function is a function $f(x)$ with the property that $f(-x)=f(x)$ for any value of $x$. The graph of $y=f(x)$ for an even function has reflectional symmetry about the $y$-axis.

Examples are $\cos x$ and $x^2$.

Note that it is possible for a function to be neither even nor odd, for example $f(x)=1+2x$.