Solve for \(\displaystyle r\)

\(\displaystyle A = (\pi)r^{2}\)

\(\displaystyle \dfrac{A}{\pi} = \dfrac{(\pi)r^{2}}{\pi}\)

\(\displaystyle \dfrac{A}{\pi} = r^{2}\)

\(\displaystyle \sqrt{\dfrac{A}{\pi}} = \sqrt{r^{2}}\)

\(\displaystyle \sqrt{\dfrac{A}{\pi}} = r\)