Simplify $($don$\text{'}$t solve$)o{\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{di{r}^2}{r^2}=q,$ where vec$(i)$ and vec$(r)$ are in the $x-y$ plane given by $r^{}$

Now some Derivatives. A derivative shows a change in a function. We will use these in $AC$ circuits.