Let $W$ be a subspace of an inner product space $V$. Show that, \begin{equation} W=(W^\perp)^\perp \end{equation}
I understand how this can work just not sure how to prove this mathematically. I know that $W^\perp=\big\{v\in V: \langle w,v \rangle=0 \space \forall \space w\in W \big\}$ but unsure what $(W^\perp)^\perp$ would be and how to use $(W^\perp)^\perp$ to prove that it is equal to $W$.