## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$\text{even}$
Definition of even and odd functions" If $f(x)=f(-x)$. then the function is even. If $f(-x)= -f(x)$ then the function is odd. Thus, if $f(x)=f(-x)$, then the function is even.