论坛 › 难题征解 › O,I为ΔABC外内心,P∈OI，PA,PB,PC交⊙O于D,E,F，证:∠BDC,∠CEA,∠AFB平分线交点∈OI

dlsh 发表于 2022-8-11 21:16:29

O,I为ΔABC外内心,P∈OI，PA,PB,PC交⊙O于D,E,F，证:∠BDC,∠CEA,∠AFB平分线交点∈OI

本帖最后由 dlsh 于 2022-8-11 22:16 编辑

http://www.mathchina.com/bbs/data/attachment/forum/202208/09/231033c9n4n242g9tolc4c.gifhttp://www.mathchina.com/bbs/data/attachment/forum/202208/09/231033c9n4n242g9tolc4c.gif
http://www.mathchina.com/bbs/data/attachment/forum/202208/07/203231k93c734g03h9554h.png
原帖这种情形是外角平分线才对

dlsh 发表于 2022-8-11 22:17:09

http://www.mathchina.com/bbs/data/attachment/forum/202208/09/231033c9n4n242g9tolc4c.gif
http://www.mathchina.com/bbs/data/attachment/forum/202208/07/203231k93c734g03h9554h.png
图片链接不出来

dlsh 发表于 2022-8-13 22:47:39

内心如何表达？如何区别两条分角线

查看完整版本: O,I为ΔABC外内心,P∈OI，PA,PB,PC交⊙O于D,E,F，证:∠BDC,∠CEA,∠AFB平分线交点∈OI