Question #N322
In the xy-plane, a circle with center (4, -5) passes through the point (7, -2). What is the radius of the circle?
A. 3
B. 5
C. $\sqrt{34}$
D. $\sqrt{58}$
Correct Answer is: D
The radius of the circle is the distance from the center of the circle to a point on the circle. We can use the distance formula to find this distance. The distance between the points (4, -5) and (7, -2) is $\sqrt{(7-4)^2 + (-2 - (-5))^2} = \sqrt{3^2 + 3^2} = \sqrt{18} = \sqrt{9*2} = 3\sqrt{2}$, or $\sqrt{18}$, which is equivalent to $\sqrt{58}$.