[填空题]
The water depth, D, iu c rf(/+r-grqn metres, in a harbour on a parghht)xpg e0e3(l xz;-ticular can be modelled by the equation x (tzpl 0ge)hxgeh3-; D=3sin($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 boat has a draught of 2.5 metres. Decide whether the boat will be able to enter the harbour at 8 pm.
