In cylindrical coordinates, <math>d^2r=rdrd\phi \quad</math>. Also, <math>\dot{A}\left(\mathbf{r},t'-\frac{|\mathbf{r}-\mathbf{r}'|}{c}\right)=\dot{A_0}e^{-ik(t'c-|\mathbf{r}-\mathbf{r}'|)}</math>. So:<br><br> | In cylindrical coordinates, <math>d^2r=rdrd\phi \quad</math>. Also, <math>\dot{A}\left(\mathbf{r},t'-\frac{|\mathbf{r}-\mathbf{r}'|}{c}\right)=\dot{A_0}e^{-ik(t'c-|\mathbf{r}-\mathbf{r}'|)}</math>. So:<br><br> |