[tex]\bf \textit{circumference of a circle}\\\\
C=2\pi r\qquad
\begin{cases}
r=radius\\
----------\\
C=4\sqrt{3}\ \pi
\end{cases}\implies 4\sqrt{3}\ \pi=2\pi r
\\\\\\
\cfrac{4\sqrt{3}\ \pi}{2\pi}= \boxed{r}\\\\
-----------------------------\\\\
\textit{area of a circle}\\\\
A=\pi r^2\qquad \boxed{r}=\cfrac{4\sqrt{3}\ \pi}{2\pi}\implies A=\pi \left( \cfrac{4\sqrt{3}\ \pi}{2\pi} \right)^2[/tex]
