The minimum depth, dft of water in a harbour t hours after midnight can be approximated by the function: d(t) = 35 + 15cos0.5t
0<= t <= 24
a) A ship with a draught of 25ft is in harbour at midnight. By what time must it leave to prevent grounding?
b) What is the next time it can return to harbour?
Answers: a) 04:36 b) 10:53
how do you do this? Thanks.