S
songlacho_dauchinhan
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
Cho tam giac ABC noi tiep (O). Goi D la 1 diem tren BC, qua D ve 2 dg` tron O1 va O2 tiep xuc lan luot voi AB va AC dj qua B va C. Goi E la giao diem thu 2 cua 2 dg` tron nay`. Chung minh: E cung thuoc dg` tron O