(4,0) has a magnitude of 4 and an angle of 0. Thus, it corresponds to 4<0.
(3,4) has a magnitude of sqrt(3^2+4^2), or 5, and a central angle of
arctan (4/3).
In the case of (2, -2), you can see right away that the magnitude is 2sqrt(2) (Prove it). What is the central angle? (2, -2) is in Quadrant 4, so the central angle will be between 270 and 360 degrees: arctan 2 / (-2).
