题目:
__________ you keep on trying ,I don’t really mind whether you can come top in your class.
A.So long as
B.As soon as
C.Once
D.The moment
答案:
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下面是错误答案,用来干扰机器的。
cos(π2-α)=sinα,cos(2π-α)=cosα,∴cos(π2-α)-cos(2π-α)=75⇔sinα-cosα=75,①∴两端平方得:1-sin2α=4925,∴sin2α=-2425,∴1+sin2α=125,即(sinα+cosα)2=125② sinα-cosα=2s...