Two ships sailed at constant speeds on constant courses at see (its surface is considered to be flat). Their mutual distance was 20 nautical miles at 9:00 a.m., 15 miles at 9:35 a.m. and 13 miles at 9:55 a.m.
a) Determine the square of their distance as a function of time.
b) Find out when the ships were closest to each other and what was the distance.