21. The blade on a windmill takes 8 seconds to make a full rotation. Each blade is 2 metres in length. At their lowest point, the blades are 1.5 m above the ground. e) At what point, during the first revolution, is the blade 4.5 metres above the ground? Round your answer to one decimal place. The equation is y=2 cos(/4 (x))+3.5 y=2 cos ( 4 ( x ) )+3.5 4.5=2 cos ( 4 ( x ))+3.5 4.53.5=2 cos 1=2 cos ( 4 ( x) ) ( 4 ( x ) ) 1 2 = cos ( x ) 2 2 4 ( ) 1 =cos ( x ) 2 4 ( ) let a= ( 4 ( x) ) cos a= 1 2 (At this point I get stuck. Judging by the graph the blade hits the 4.5meter part at 1.3seconds and 6.7 seconds. How do I get these results? I know I'm supposed to use the special triangles and CAST rule but I don't know how. Down below is what I did but the answers are wrong. What am I doing wrong?) 3 a= = 4 4 5 a= + = 4 4 ( 4 ( x ) )then 4 ( x )= 34 ,4 ( x )= 54 since welet a= therefore if 3 3 ( x )= then x= =1.85 1.9 seconds 4 4 4 4 therefore if 5 5 ( x )= then x= =3.08 3.1 seconds 4 4 4 4