Suppose you want to expand this ground state in a Fourier series. As a first step, set up the integrals for the Fourier coefficients.
Now do some sensemaking. Which terms will have the largest coefficients? Explain briefly.
More sensemaking: Are there any coefficients that you know will be zero? Explain briefly.
Now calculate: Using the technology of your choice or by hand, calculate the four largest coefficients. With screen shots or otherwise, show your work.