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yennhimachiko
2 năm trước
cho tam giác ABC vuôgn góc tại A có góc B = 60 độ, BC=6cm, đường cao AH a, trên tia đối của tia BA lấy điểm D sao cho BD=BC chứng minh AB/BD=AC/CD b, từ A kẻ đường thẳng song song với phân giác của góc CBD cắt CD tại K chứng minh 1/KD.KC=1/AC^2 + 1/AD^2
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