[填空题]
The tip of a large wind turbine's blade rotate hpu *.y.1x-g pbtrto4s at a constant speed on a wiy y jh6 e:ep7amuh r4 ,eslf98xwk+r1*ndy day. Its hei8k :f1xu47,ypaeee * 9ljymhw rs+hr6ght, $H$ , 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.
