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tramanh1111
2 năm trước
cho tam giác ABC vuông tại A. Gọi E và D lần lượt là trung điểm của các cạnh AB và AC; G là giao điểm của CE và BD; H và K là trung điểm của BG và CG. a) Tứ giác DHEK là hình gì? Vì sao? b)Tính diện tích tam giác ABC biết AB=3cm, AC=4cm. c) Tam giác ABC có điều kiện gì thì tứ giác DEHK là hình chữ nhật.
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