Chapter 17.5, Problem 19E

Divergence of radial fields Calculate the divergence of the following radial fields. Express the result in terms of the position vector r and its length |r|. Check for agreement with Theorem 17.10

19. $F=\frac{\langle x,y,z\rangle }{{\left(x^2+y^2+z^2\right)}^2}=\frac{r}{{\left|r\right|}^4}$