Chapter 22, Problem 72P

Using the dipole potential at points far from a dipole (given by Equation 22.6 in Example 22.5), show that the electric field at an arbitrary position can be written

$\stackrel{\to }{E}=\frac{kp}{r^3}\left[\left(3{\cos }^2\theta -1\right)\hat{i}+3\sin \theta \cos \theta \hat{j}\right]$

where the x-axis coincides with the dipole axis.