[填空题]
The tip of a large wind turbine'sd17 yf bfsik4/, ku-lyrdn9x9 4 xp0b- qc8cxl blade rotates at a constant speed on a windy day. Its heix 4cqnclr- -d98l,k0ybxu p9 xght, $H$ , 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.
