[填空题]
The water depth, D, in metres, in a harbour on 55wy9;+e v w(qb ,b-:qhscn vyeond5zw ot-t(a particubm*i1 d+d hm vqnymro5t2)o).lar day can be modelled by the equation.otv yi) *)5rhdd1nobqm +2m m 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.
