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Quynhbi
2 năm trước
b1:Cho tam giác ABC không có góc tù. Các đường cao AH và đường trung tuyến AM không trùng nhau. Gọi N là trung điểm của AB. Cho biết BAH CAM = . a) Chứng minh tứ giác AMHN nội tiếp. b) Tính số đo của góc BAC b2:Cho tam giác ABC vuông tại A. Điểm E di động trên cạnh AB. Qua B vẽ một đường thẳng vuông góc với tia CE tại D và cắt tia CA tại H. Chứng minh rằng: a) Tứ giác ADBC nội tiếp. b) Góc ADH có số đo không đổi khi E di động trên cạnh AB. c) Khi E di động trên cạnh AB thì BA.BE+CD.CE không đổi. mình cảm ơn trc nha
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