1) If you have a particle in 1D bound within range "-a" and "a". You come up with one eigenfunction that is sinusoidal (since it satisfies the problem). Now, you get all the necessary constants through the usual way... I want to know whether more than one eigenfunction can be produced and how? Because in the end I need to show that these eigenfunctions are orthogonal. 2) If your given an eigenfunction say: psi = b(a - |x|) what does it mean by "expanding psi in eigenstates of momentum". Please note these are Intro questions to QM and I cannot read/understand DIRAC notation or any other type of that nature just yet.