You are given= -1. From it, you conclude that 45° - = 135° (a) or 45° - = 315° (b) From (a), you have = 45° - 135° = -90°, which geometrically is the same as 270°. From (b), you have = 45° - 315° = -270°, which geometrically is the same as 90°. So, you conclude that the problem has two solutions: = 90° or = 270°. ANSWER