Respuesta :

[tex]d= \sqrt{(7-3)^2+(-1-5)^2} = \sqrt{16+36} = \sqrt{52} =2 \sqrt{13} \\ \\ r= \frac{d}{2}= \frac{2 \sqrt{13} }{2} = \sqrt{13} [/tex]

the length of a radius of the circle is √13