Orthonormality of Infinite Square Well States: Prove that the eigenstates of the particle in the infinite square well are orthonormal to one another. That is, prove that if the box extends from x = 0 to x = L, the wave functions ψ_n(x) satisfy
∫_0^L ψ_n^*(x) ψ_m(x) dx = δ_mn
Here, δ_mn is the Kronecker-delta function. It is equal to 0 if n ≠ m and 1 if n = m. Since the wavefunctions are normalized by construction, it is sufficient to demonstrate only the case when n ≠ m in order to complete the proof.
Hint: You may find it easiest to use Euler's identity to write the wavefunction in terms of complex exponentials, using the results from problem 4 and thereby simplifying the integrations.