已知cos(x-y)cosx+sin(x-y)sinx=3/5,则cosy的值为
人气:210 ℃ 时间:2019-08-19 21:45:01
解答
cos(x-y)cosx+sin(x-y)sinx=cos(x-y-x)=cos(-y)=cosy=3/5
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