Prove that the normalization constant of the 1 s radial wave function of the hydrogen atom is $\left(\pi a_{\mathrm{B}}^{3}\right)^{-1 / 2},$ as given in Equation 42.7 Hint: A useful definite integral is $$\int_{0}^{\infty} x^{n} e^{-a x} d x=\frac{n !}{\alpha^{n+1}}$$