①：已知sin(π+α)=-1/3,求cos(5π+α)的值；②：已知sin(π/3+α)=-1/2,求sin(α-5π/3)的值_数学解答 - 作业小助手

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①：已知sin(π+α)=-1/3,求cos(5π+α)的值；②：已知sin(π/3+α)=-1/2,求sin(α-5π/3)的值.

人气：352 ℃　时间：2020-04-10 19:32:41

解答

cos(5π+a)=cos(π+a)=+ - 2根号2/3
sin(a-5π/3)=sin(a-5π/3+2π)=sin(a+π/3)=-1/2

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