If $Lu = u^{\prime\prime}+\omega^2u$, show that $L$ is formally self-adjoint and the concomitant is $J(u,v)=vu^\prime-uv^\prime$. Moreover, if $u$ is a solution of $Lu=0$ and $v$ is a solution of $L^*v=0$, then the concomitant of $u$ and $v$ is a constant.
I believe I can take $L$ to be a differential operator.
I'm really new to this concomitant stuff and don't understand it. Any help would be very much appreciated.