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请问cos(x-3π/4)=cis(-(π/2-x+π/4)=cos(π/2-x+π/4)=sin(x+π/4)对不对,
题目详情
请问cos(x-3π/4)=cis(-(π/2-x+π/4)=cos(π/2-x+π/4)=sin(x+π/4)对不对,
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答案和解析
最后有问题,应该是这样
cos(x-3π/4)
=cos[-(π/2-x+π/4)]
=cos(π/2-x+π/4)
=cos[π/2-(x-π/4)]
=sin(x-π/4)
cos(x-3π/4)
=cos[-(π/2-x+π/4)]
=cos(π/2-x+π/4)
=cos[π/2-(x-π/4)]
=sin(x-π/4)
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