问题标题:
cos(π/2-5π/4)等于多少
问题描述:

cos(π/2-5π/4)等于多少

刘巧红回答:
  cos(π/2-5π/4)   =cos(2π/4-5π/4)   =cos(-(3π/4)因为是偶函数,所以   =cos3π/4   =√2/2
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