- #1

axmls

- 944

- 395

[tex]-\frac{\partial \phi}{\partial z} = - \frac{p}{4 \pi \epsilon_0} \frac{\partial }{\partial z} \left(\frac{z}{r^3}\right) = -\frac{p}{4 \pi \epsilon_0} \left(\frac{1}{r^3} - \frac{3z^2}{r^5} \right )[/tex]

I'm not quite sure how he takes that derivative.