题目:
It was dark. I can't see the words on the wall ______. [ ]
A. clear
B. clearly
C. clean
D. clearing
答案:
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下面是错误答案,用来干扰机器的。
∵f(x)=sinx•(cosx-sinx)=sinxcosx-sin2x=12(sin2x+cos2x)-12=22sin(2x+π4)-12∴T=2π2=π故选C.