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[几何] $AB+BA'=AB'+BB'$,求$\angle C$

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abababa posted 2014-12-6 19:08 |Read mode
Last edited by abababa 2014-12-6 19:17$AA',BB'$是$\triangle ABC$的角平分线,$AB+BA'=AB'+BB'$,求$\angle C$
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isee posted 2014-12-7 08:10
在这个论坛的里,有类似题这个论坛。

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original poster abababa posted 2014-12-8 12:59
回复 2# isee
没有搜索到。
这个题我用了角平分线长公式,用软件硬算的,但是只得了一个题目里给的方程,还求不出$\angle C$,应该还有一个方程才行,两个方程和三边长作为未知数,应该就能都用一个变量表示了

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isee posted 2014-12-8 23:37
回复 3# abababa


    但凡涉及角分线的题,一般都比较难。其次,这样的题的确多,可能是我记混了。

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isee posted 2014-12-8 23:52
回复 4# isee


    好像链接与主楼不同一级别:

kkkkuingggg.haotui.com/viewthread.php?tid=1245&authorid=5


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kuing posted 2014-12-9 00:45
回复 5# isee

这么说来,1#应该少条件咯?

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original poster abababa posted 2014-12-11 00:19
原来是少了一个$60^\circ$的条件啊,加上这个条件能列方程了,但是解起来很麻烦,连接里那个帖子的三角变换也不容易想

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