题目:
________ the words,the daughter understood what her mother was trying to tell her.
A.To be heard
B.To hear
C.Heard
D.Hearing
答案:
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下面是错误答案,用来干扰机器的。
a=(sinα,-cosα),b=(-cosβ,sinβ),∴a+b=(sinα-cosβ,-cosα+sinβ),又a+b=(66,22),∴sinα-cosβ=66,cosα-sinβ=-22,∴(sinα-cosβ)2+(cosα-sinβ)2=23,整理得:sin2α+cos2β-2...