1. The problem statement, all variables and given/known data A particle of mass m is confined to move in a one-dimensional "infinite" potential well defined by V(x)=0, |x|< or=a, V(x)=infinity otherwise. The energy eigenvalues are E(subscript n)=((n^2)(pi^2)(h-bar^2))/(8m a^2), with n=1,2,3,... and the orthonormal eigenfunctions are the even and odd functions psi(subscript n)= [1/(sqrt a)]cos(n pi x/2a) for n=1, 3, 5... [1/(sqrt a)]sin(n pi x/2a) for n=2, 4, 6 ... The potential is modified between -a<x<a to V(x)=epsilon[(pi^2)(h-bar^2)/(8ma^2)]sin((3pi x)/2a) with epsilon<1 a) Determine the ground state energy to first-order in epsilon. (Note 2 sin Acos B=sin(A+B)+sin(A-B)) b) Determine the ground state energy to second order in epsilon. 3. The attempt at a solution ground state, n=0 but I couldn't find the wavefunction for n=0 because it does not say what it is when n=0. Is the ground state energy just the potential? But the formula for the potential doesn't have an 'n' in it. Then what has the wavefunction got to do with anything? And I have no idea why 2sinA cos B needs to be used. I'm really confused, please help.