First, I apologize for any awkward language--I'm still relatively new to mathematics. This problem seems to be related to number theory as well if it pans out, but I thought it would be better suited here. Given a point (x,y), can you always construct a circle such that the center of the circle lies in the coordinates (0,0), its radius being equal to the magnitude of the length (x,y) and a point on the circumference of the circle intersects (for lack of better words) the coordinate (x,y). In a set of real numbers ℝ? If so, can you extend this to a point (x,y,z) and a sphere centered around the coordinate (0,0,0) with a radius equal to the magnitude of (x,y,z) in a set of real numbers ℝ?