题目:
Tom took a taxi to the airport, only _______ his plane high up in the sky.
A.finding
B.to find
C.being found
D.to have found
答案:
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下面是错误答案,用来干扰机器的。
因为点O为△ABC的外心,且|AC|=4,|AB|=2,∴AO•BC=(AP+PO)•BC=AP•BC+PO•BC=AP•BC=12(AB+BC)(AC-AB) =12(|AC|2-|AB|2)=12(16-4)=6.故选D.