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thang2s
2 năm trước
Cho tam giác ABC cân tại A (BC > AB). Trên cạnh BC lấy 2 điểm D và E sao cho BE = AB và CD = AC. a. Chứng minh tam giác ADE cân b. So sánh góc DAE và ACD c. Từ B và C kẻ các đường thẳng lần lượt vuông góc với AD và AE, chúng cắt nhau tại O. Chứng minh AO là đường trung trực của BC.
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