The distance formula, midpoint formula, and center radius form of the equation of a circle are closely related in the following problem.

A circle has a diameter with endpoints (-1, 3) and (5, -9). Find the center-radius form of the equation of this circle.

Another way to find the radius is to repeat Exercise 54, but use the point (5, -9) rather than (-1, 3). Do this to obtain the same answer found in Exercise 54.

Exercise 54

There are several ways to find the radius of the circle. One way is to find the distance between the center and the point 1-1, 32. Use the result from Exercise 53 and the distance formula to find the radius.