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春芽
共回答了23个问题采纳率:91.3% 举报
(1)作AG∥BC交BE的延长线于点G,
∴AE/EC=GE/EB=AG/BC=1/2
∵BC=2BD
∴AG/BD=1/1
∵AG∥BD
∴AF/FD=AG/BD=1/1
(2)若AE/EC=1/3,AG/BC=AE/EC=1/3
∴AG/2BD=1/3
∴AG/BD=2/3
∵AG∥BD
∴AF/FD=AG/BD=2/3
(3)若AE/EC=1/k,
∵AG∥BC
∴AG/BC=AE/EC=1/k
∵BC=2BD
∴AG/BD=2/k
∵AG∥BC
∴AF/FD=AG/BD=2/k
1年前
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