[填空题]
Two identical water waves pass a sensor in an oceanmvvzgi l9p;m 79zer4c (j.ar :ography laboratoroic7 a h/)7 8pq w/as-kssq+32 rygipzy8f 8jey. As the waves pass the sensor, the depth, D, in metres, of water is r-q3 /+7 gac p7i 8f2/psz8e oyiawsj )hqsyk8recorded and modelled by the function
D(t)=3.21−0.45cos($24.2^{\circ}$$\times$t)
where t is the elapsed time, in seconds, since the first wave hit the sensor.
1.Find the minimum and maximum depths of the water as the two waves pass the sensor.$D_{min}$ = ; $D_{max}$ =
2.Find the first time after 1616 seconds at which the depth of water reaches 3.5m. t ≈
