[填空题]
The water depth, D, in metreho9upq 8vr;st h:j9c1 s, ix9o1pi0wrb; i,:sro; y9bkjqbx wu +- n a harbour on a particular day can be modelled by the equa:;+9;r0wwbbs i,bpoi r ok 9uxjx- 1yqtion
D=2.5cos($30^{\circ}$$\times$t)+5, 0≤t≤24,
where t is the elapsed time, in hours, since midnight.
1.Draw the graph of D versus t on the grid below.
2.Find the lowest and highest depths of water in the harbour, and the times when they occur. $D_{min}$ = t = ; $D_{max}$ = t =
3.A large yacht has a draught of 3 metres. Decide whether the yacht will be able to enter the harbour at 5 pm.
