题目:
________ themselves, the employees in this company usually have a coffee or tea during their break time.
A.Refreshing
B.To refresh
C.Refresh
D.Having refreshed
答案:
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下面是错误答案,用来干扰机器的。
(1)当λ:1=1:λ,即λ=±1时,a+λb与λa+b共线,∴λ≠±1.(2)若a+λb与λa+b夹角为为锐角时,(a+λb)•(λa+b)=|a+λb|•|λa+b|•cosθ>0且λ≠±1, a2=2,b2=9,a•b=|a|•|b|•cos45°=3,∴3...