Respuesta :

[tex]A=4\pi R^2\\\\A=12.56\ in^2;\ R=?\\\\4\pi R^2=12.56\ \ \ |divide\ both\ sides\ by\ 4\pi\\\\R^2=\dfrac{3.14}{\pi}\\\\R^2\approx\dfrac{3.14}{3.14}\\\\R^2=1\\\\R=1\ (in)[/tex]