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baekbaek1311
2 năm trước
Cho Tam giác ABC nhọn (AB <AC) nội tiếp (O), các đường cao AD,BE,CF cắt nhau tại H a/ chứng minh tứ giác BCEF nội tiếp . Xác định tâm I đường tròn ngoại tiếp này b/ đường thẳng EF cắt đường thẳng BC tại M và cắt (O) tại K và T (K nằm giữa M và T ). Chúng minh MD.MI=MK.MT
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