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[几何] $E$是$OI$的中点，求证$DE \perp MN$

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abababa Post time 2014-12-26 09:10 |Read mode

如图，$AD,BM,CN$都是角平分线，$O,I$分别是外心和内心，$E$是$OI$的中点，求证$DE \perp MN$
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isee Post time 2014-12-26 10:24

kuing.cjhb.site/forum.php?mod=viewthread&tid=2604

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Author| abababa Post time 2014-12-26 22:31

回复 2# isee
谢谢，也问了一位网友，他的证明看不懂，2楼这个勉强看进去了，对我来说太难了

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