An equation of circle has form
[tex](x-x_0)^2+(y-y_0)^2=r^2 \\ where\: x_0\: and\: y_0\: are\: the\: center[/tex]
So, the center is (13;1)
Now we need to find a radius
Let's create an equation
[tex] {r}^{2} = 4 \\ r = \sqrt{4} \\ r = 2[/tex]
So radius is 2