A)cota=2cotb
B)tana=2tanb
C)cota=2/3cotb
D)tana=2/3tanb
更新1:
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maths難唔識~~中六,七maths題~
2007-12-24 1:17 am
若正三棱錐的側棱和側面分別與底面成a角和b角,則一定有
A)cota=2cotb
B)tana=2tanb
C)cota=2/3cotb
D)tana=2/3tanb
A)cota=2cotb
B)tana=2tanb
C)cota=2/3cotb
D)tana=2/3tanb
回答 (3)
2007-12-24 2:27 am
✔ 最佳答案
圖片參考：http://img254.imageshack.us/img254/1840/pic01jk1.gif
圖中為一正三棱錐，∠ACF = a，∠AEF = b
AF為此棱錐的高 h
△AFC、△AEF和△CEF均為直角三角形，∠ACF、∠AEF和∠CEF = 90°。
設FE = x
FC = FE/sin FCE = FE/sin (60°/2) = 2x
△ACF，cot a = CF/AF = 2x/h
(1/2)cot a = x/h
△AEF，cot b = EF/AF = x/h
cot b = x/h
∴(1/2)cot a = cot b
cot a = 2cot b
ANS : A) cota=2cotb
2007-12-24 1:44 am
B)tana=2tanb
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參考: me
2007-12-24 1:20 am
收錄日期: 2021-04-24 08:03:12
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071223000051KK02627