Prove that if $\displaystyle p \equiv 3 (\mod{8})$ and $\displaystyle (p-1)/2$ is prime then $\displaystyle (p-1)/2$ is a quadratic residue $\displaystyle (\mod{p})$.

I believe I need to show that $\displaystyle (((p-1)/2)/p) = 1$. Will someone show me where to start? I have been thinking about this problem all weekend.

Thanks in advance,