1. The problem statement, all variables and given/known data Here's something that's confusing me. Say we have a potential V(x) = Vo if x < 0, x > a and V(x) = 0 if 0 < x < a (yes I know the notation with greater than/equals etc isn't totally correct, but you know what I'm talking about.) In the middle section, ψ'' + k2ψ = 0 Whenever I see the solutions it's always ψ = Asin(kx) + Bcos(kx) in the middle section where k2 = -2mE/h2 In the right/left sections, ψ'' + f2ψ = 0, with f2 = -2m(E - V0)/h2 The solutions here always seem to be complex exponentials. Can someone please explain the difference to me in the solutions?