Show f(x) can be expressed as the sum of E(x) and an odd function O(x).

f(x) is defined for all x (assume domain D symmetric about 0)

$\displaystyle E(x) = \frac{f(x) + f(-x)}{2}$

$\displaystyle f(x)$ is even if $\displaystyle f(x) = f(-x)$

$\displaystyle f(x)$ is odd if $\displaystyle f(x) = -f(x)$

I'm not quite sure how to begin doing that.