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已知sin(α+π/12)=1/3,求cos(α+7π/12)的值
人气:447 ℃ 时间:2019-12-18 21:57:28
解答
令x=α+π/12
则α=x-π/12
且sinx=1/3
所以原式=cos(x-π/12+7π/12)
=cos(x+π/2)
=*-sinx
=-1/3
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