A tower is 203 metres away from a 1.6 metre height spectator. From his eye to the top of the tower, the angle of elevation is 30 degrees. The tower stands at the following height:
A. 21.6 m
B. 23.2 m
C. 24.72 m
D. None of these
Answer:A
A tower is 203 metres away from a 1.6 metre height spectator. From his eye to the top of the tower, the angle of elevation is 30 degrees. The tower stands at the following height:
A. 21.6 m B. 23.2 m C. 24.72 m D. None of these
Explanation: Assume the observer is AB, and the tower is CD.BE CD should be drawn,CE = AB = 1.6 m, BE = AC = 203 m, and so on, DE/BE = tan 30° = 1/ ROOT 3 DE =20 ROOT 3/ ROOT 3 m = 20 m DE/BE = tan 30° = 1/ ROOT 3 DE =20 ROOT 3/ ROOT 3 m = 20 m, CD = CE + DE = (1.6 + 20) m = 21.6 m