[填空题]
The water depth, D, in metres, jx.)opt*pox6 io4gb .ry)a j8ij cwa 9x.q3gjm/sn2u7 81 zpabn a harbour on a particular day can be modelled 81cgu aq /j mps92.ajw3z xnb7by the equation
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.
