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[几何] 两个三角形内心外心证明垂直

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hbghlyj Posted 2020-6-15 18:42 |Read mode

在△ABC中，D为BC边上一点，设△ABD,ACD的内心为$I_1,I_2$，△$AI_1D,AI_2D$的外心为$O_1,O_2$，$I_1O_2$与$I_2O_1$交于P,求证PD⊥BC
source:2017西部奥林匹克

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Author| hbghlyj Posted 2021-1-27 13:36

下面是一个类似题(不会做)
facebook.com/groups/parmenides52/permalink/2571722686274755
garciacapitan.blogspot.com/2019/11/an-insanely-huge-locus.html

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