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hovang49
![](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 vuong can tai A , AB=AC=4 cm. Lay diem D tren AB. Qua D ve duong thang vuong goc voi AB cat BC tai E. Qua E ve duong thang vuong goc voi AC cat AC tai F. Xac dinh diem D tren AB de ADEF co dien tich lon nhat