Using the method of separation of variables on the equation mm + uyy = 0 for the square 0 S gr: 5 2n, 0 g y 5 2n, we find equations X\" + AX = 0 and Y\" AY = 0 with boundary conditions X(0) = X(27r) = 0, and Y(0) = 0. Find the eigenvalues and eigenfunctions and write the Fourier series for ML y)