Three circles of common radius, r, are drawn through a common point, P. A three-point circle, C, is drawn through their pairwise points of intersection.
Determine the radius of C.
Well, let the three points of intersection be x,y, and z. If Angle xPy = Angle xpz = Angle yPz = 120 degrees, then
r = radius of C and P = the center of C.
Other configurations of the three circles are possible, and it is not clear whether the radius of C is always equal to r.