OpenSAT

The radius of the circle is the distance between the center of the circle and any point on the circle. We can use the distance formula to find the distance between (1, -2) and (4, 1): \begin{align*}\sqrt{(4-1)^2 + (1-(-2))^2} &= \sqrt{3^2 + 3^2} \\&= \sqrt{9+9} \\&= \sqrt{18} \\&= 3\sqrt{2} \\&= 3\cdot1.414 \\&= 4.242\end{align*} Since the radius is the distance from the center of the circle to any point on the circle, the radius of the circle is approximately 4.242. Of the given choices, 5 is closest to 4.242. Therefore, the radius of the circle is approximately 5.