Cho tam giác ABC có góc A = 1v. Trên AC lấy điểm M sao cho AM<MC. Vẽ đường tròn tâm O đường kính CM; đường thẳng BM cắt(O) tại D; AD kéo dài cắt (O) tại S a.Chứng minh BACD nội tiếp b. BC cắt (O) tại E. Chứng minh rằng : MD là phân giác của góc AED c. Chứng minh CA là phân giác của góc BCS

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