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hanphamng08
2 năm trước
Cho tam giác ABC cân tại A. Gọi E,F lần lượt là trung điểm của AB,AC. a) Tính độ dài EF biết BC = 12cm b)Lấy điểm I là trung điểm BC. C/m tứ giác IEFC là hình bình hành. c) Kẻ BH vuông góc với AC tại H. C/m tứ giác EFHI là hình thang cân.
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