This is a question for those with Shankar in their disposal. When studying from this book, Exercise 5.1.1 puzzled me. Now, it is easy to solve the exercise from 5.1.9. However, how would we expand psi in terms of the energy eigenfunctions,* if we did not have 5.1.9*, but instead started fresh? It seems to me that the factor of m/(2mE)^(1/2) would then be absent from our integrand, instead of being the same as the integrand in Exercise 5.1.1. Can somebody shed some light on this confusion of mine? Thanks.