Find the equations that describe the circle of radius 3 centered at (4, 2, 5) that is parallel to the xy-plane. (enter your answers as a comma-separated list of equations.)

We have that the coordinates given are for a sphere.
 As we look for a circle parallel to the xy plane, then our xy coordinates are:
 (x, y) = (4, 2)
 The standard equation of the circle is:
 (x - h) ^ 2 + (y - k) ^ 2 = r ^ 2
 where h and k are the x and y coordinates of the center of the circle and r is the radius.
 We have then:
 h = 4
 k = 2
 r = 3
 The equation of the circumference is:
 (x - 4) ^ 2 + (y - 2) ^ 2 = 9
 answer
 (x - 4) ^ 2 + (y - 2) ^ 2 = 9