1. A sailboat race course consists of four legs, defined by the displacement vectors A, B, C, and D, as the drawing indicates. The magnitudes of the first three vectors are A = 3.20 km, B = 5.10 km, and C = 4.80 km. The finish line of the course coincides with the starting line. Using the data in the drawing, find the distance of the fourth leg and the angle θ.
