To add to my attempt at a solution:
<L3> = <Lz> = integral(-inf to inf of(psi* x L3operator x psi dz)
L3 operator = (-i x hbar) x (partial / partial x phi)
Homework Statement
Consider wavefunction psi (subscript "nlm") describing the electron in the stationary state for the hydrogen atom with quantum numbers n,l,m and the third component L3 for the orbital angular momentum operator L. What is the expectation value of L3 and of L3^2 for the...