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本期问题 初99 在△ABC中,AB=AC,CD是高,DM⊥BC、DN⊥AC,M、N都是垂足。当CD=DM+DN时,求(AB)/(BC)。
In this issue, at the beginning of 99, in △ABC, AB=AC, CD is high, DM ⊥BC, DN⊥AC, and M and N are all feet. When CD=DM+DN, find (AB)/(BC).