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ha0359504
2 năm trước
cho tam giác ABC cân tại a (góc a<90°).Kẻ BD vuông góc AC (D€AC), kẻ CE vuông góc AB (E€AB). chứng minh rằng AD=AE b,gọi I là Giao điểm của BD và CE.CHỨNG minh AI là tia phân giác góc A c, tính độ dài BC, biết AD=7cm DC=1cm
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