Respuesta :
[tex]\bf \textit{circumference of a circle}\\\\ C=2\pi r~~ \begin{cases} r=radius\\[-0.5em] \hrulefill\\ C=13\pi \end{cases}\implies 13\pi =2\pi r\implies \cfrac{13\pi }{2\pi }=r\implies \boxed{\cfrac{13}{2}=r} \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ \textit{area of a circle}\\\\ A=\pi r^2\qquad \qquad \implies A=\pi \left(\cfrac{13}{2} \right)^2\implies A=\pi \left( \cfrac{13^2}{2^2} \right)\implies A=\cfrac{169}{4}\pi[/tex]
