幾何 勾股 逆勾股 求救 急
2011-11-04 5:05 am
圖片參考：http://imgcld.yimg.com/8/n/HA07870362/o/701111030079313873396730.jpg
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回答 (2)
2011-11-04 6:40 am
✔ 最佳答案
AB^2 = AC^2 + BC^2 26^2 = 10^2 + BC^2
BC^2 = 676 - 100 = 576
so BC = sqrt 576 = 24.
Let angle DAC = x
tan 2x = BC/AC = 24/10 = 2.4
tan x = CD/BC = d/10
so tan 2x = 12/5 = 2(d/10)/[1 - (d/10)^2]
12/5 = (d/5)/[1 - d^2/100]
12/5 = 20d/(100 - d^2)
12(100 - d^2) = 100d
300 - 3d^2 = 25d
3d^2 + 25d - 300 = 0
(3d - 20)(d + 15) = 0
d = - 15 (rej.) or 20/3
so BD = BC - CD = 24 - 20/3 = 52/3 cm.
2011-11-05 4:56 am
2 2
26 -10
=676-100
2
=576(cm )
2011-11-04 20:59:42 補充：
2 2
26 -10
2011-11-04 21:06:38 補充：
26 2-10 2
26 -10
=676-100
2
=576(cm )
2011-11-04 20:59:42 補充：
2 2
26 -10
2011-11-04 21:06:38 補充：
26 2-10 2
參考: I
收錄日期: 2021-04-13 18:20:57
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20111103000051KK00793