Re: [中學] 三角幾何
※ 引述《callmedance (NightFury)》之銘言：
: http://ppt.cc/v6nj
: 卡題…試過內分比跟面積沒整理出來
令AK = z
AB = x
BK = ax
∠AKC = t
z^2 + a^2 - 2azcost = 1
z^2 + a^2 x^2 + 2ax^2 zcost = x^2
=> z^2(x + 1) + xa^2(1 + x) = x(1 + x)
=> z^2 + xa^2 = x
=> 1 + a^2 - a = x(1 - a^2)
=> x = [1 - a + a^2]/[1 - a^2]
= -1 + (2 - a)/(1 - a^2)
=> BC = ax + a = a(x + 1) = a(2 - a)/(1 - a^2)
結果就是這樣
沒有那麼難看
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※ 編輯: Honor1984 (220.141.65.137), 05/09/2014 20:18:01
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05/10 00:27, , 1F
05/10 00:27, 1F
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