[填空题]
The tip of a large wind turbine's blade rotatekf: gtpw75 9avc8pfwg s; ;7ncs at a constant speed on a*, rwlav9* la h3a3bhr,qepo. windy day. Its hea3a,hpr * ael,w*rblho 9.qv 3ight, $H$ , in metres, above the ground is modelled by the function
H(t)=52sin(60$^{\circ}$$\times$t)+80,where $t$ is the elapsed time, in seconds, since the turbine was accelerated to its max speed.
1.Write down the minimum height of the blade's tip above the ground. $H_{min}$ = m
2.Find the height of the blade's tip above the ground after 88 seconds. H = m
3.Find the time it takes for the blade's tip to complete one full revolution.
