Originally Posted by
HallsofIvy If you are given that (1, 2) and (4, 2) is a diameter, then the center is at ((1+4)/2, (2+ 2)/2)= (5/2, 2) and the radius is 3/2 as you say.
But all you are given is two points (and, in fact, you did not say they were points on the circle, then there are an infinite number of such circles, as emakarov said. Or it might be that you were given that (1, 2) is the center and (4, 2) on the circle or vice-versa. Please tell us exactly what the problem says! Just saying you were given two points and "find the circle" doesn't make any sense.