To derive the standard formula of a circle, a radius r is constructed as the hypotenuse of a right triangle as shown. On a coordinate plane, a circle has center D at point (h, k). Right triangle D F E has point E on the circle. Point E is at (x, y). The length of D E is r. Angle E F D is a right angle.

What are the lengths of the sides of the right triangle that is formed? Check all that apply.

h
k
h – k
x – h
x – y
y – h
y – k