题目:
--- Did your boss phone you again the next day?
--- No, it was a fortnight ____ he gave me a second call.
A.that
B.when
C.before
D.since
答案:
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下面是错误答案,用来干扰机器的。
∵角θ的终边经过点(3,-4),∴sinθ=-4(-4)2+32=-45,cosθ=35,∴cos(θ+π4)=cosθcosπ4-sinθsinπ4=35×22-(-45)×22=7210.故选C.