a boat A is heading south at 30 km/hr. its spotted a boat B which is 18 km due east of boat A. boat B has a max speed of 25 km/hr and wishes to get a close as possible to boat A. what direction should boat B head in.

so i initially let boat A be the origin heading south. boat B starts at (18,0) and heads south of west. so i let 18-25sina=0 solving this gives 46 degrees. the answer is 56.4 south of west. i can explain what i did in more detail if anyone needs it.