標題:

Maths problems!!!!!!!!!!!!!!!!

發問:

13. In the figure, AD is the altitude from A to the side BC produced. Angle CAB=15 degrees, Angle ACD=60 degrees, BC = 100 and AD=h. (a)Express BD and CD in terms of h. (b)Hence, find the value of h.

最佳解答:

001 is wrong about ∠ABD a) CD = h / tan 60 ∠ABD = 15 + 60 = 75 (ext. ∠ of triangle ABC) BD = h / tan (180 - ∠ABD) = h / tan 75 b) CD - BD = BC h / tan 60 - h / tan 75 = 100 h x tan 75 - h x tan 60 = 100 x tan 60 x tan75 h = 323.205

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其他解答:

i guess the 15 degree is angle ABD, right^^? (a) tan ABD = AD / BD so, BD = h / tan 60 = h / root(3) and, tan ACD = AD/ CD so, CD = h / tan 15 (b) BC = BD + CD so, BC = h / root(3) + h / tan 15 100 = h* ( 1/root(3) + 1/tan 15 ) so, h = 100 / ( 1/root(3) + 1/tan 15 ) = ... (禁機~) 2009-06-07 20:29:22 補充： 原來係咁樣~ 你(a) part tangent果度唔駛 "180 - ", 不過係小問題黎je~ 同埋, (b) part 可以抽 h 出黎, 成個 ( 1/ tan - 1/ tan ) 除過去, 會快D的 :P 2009-06-07 20:30:23 補充： 002 manyu_yan 的答案確實最佳呢~|||||Can you provide the figure?FAD2A23AB937987B
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