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hoanganhvu741852963
2 năm trước
Cho tam giác ABC có AB = AC, Â𝐴̂< 90° . Vẽ BD ⊥AC tại D, CE ⊥AB tại E. Gọi I là giao điểm của BD và CE. Chứng minh rằng: a) AD = AE b) AI là tia phân giác của góc BAC c) DE //BC, AI⊥DE d) Ba điểm A, I, M thẳng hàng (với M là trung điểm cạnh BC).
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