# Maxwell Equations: how to obtain the two zeroes and solution

#### Tan Tom

##### New member
Good evening,

How did we obtain the two zeros in the below equation and solution? Thank you.

#### topsquark

##### Full Member
Since you are working in cylindrical coordinates r, $$\displaystyle \phi$$, and z are independent variables. So by definition of partial derivatives
$$\displaystyle \dfrac{\partial z}{\partial r} = \dfrac{\partial r}{\partial \phi} = 0$$

This is identical in concept to $$\displaystyle \dfrac{\partial y}{\partial x} = 0$$ in rectangular coordinates.

-Dan