F.3 maths Trigonmetry3
2009-08-07 2:29 am
圖片參考：http://img43.imageshack.us/img43/8576/444w.jpg
In the figure, the angles of depression of points A and B from the top a building CD are 30 and 48 respectively.If A and B lie on the same plane and 150 m apart, find the height of the building correct to 4 significant figures.
回答 (1)
2009-08-07 2:38 am
✔ 最佳答案
ㄥCBD = 48 , CD/BD = tan 48 , BD = CD/tan48
ㄥCAD = 30 , CD /AD = tan 30, AD = CD/tan30,
AD - BD = AB = 150
CD/tan30 - CD/tan48 = 150
CD ( 1/tan30 - 1/tan48) = 150
CD = 124.7m(4 significant fig.)
2009-08-06 18:43:39 補充：
Corrections:
CD ( 1/tan30 - 1/tan48) = 150
CD = 150 / (1/tan30 - 1/tan48)
CD = 180.365... = 『180.4m (4 significant fig.)』
Sorry!
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https://hk.answers.yahoo.com/question/index?qid=20090806000051KK01944