I know this is an easy question but I want to confirm that I've got this right. The wavefunction [tex]\psi(r)[/tex] can be expressed as a linear sum of orthonormal eigenfunctions [tex]\phi_n(r)[/tex] by [tex]\psi(r) = \sum a_n\phi_n(r)[/tex]. Derive an expression for the coefficients [tex]a_n[/tex]. I think the answer is [tex] a_n = <\phi_n|\psi>[/tex] but this seems a little too easy. Opinions? Thanks, C.