âµÎ±â(3Ï/2ï¼2Ï)
â´cosα>0
åâµsinα=-2/3
â´cosα=â(1-sin²Î±)=â5/3
â´sin(Ï/3+α)
=sin(Ï/3)cosα+cos(Ï/3)sinα
=â3/2*(â5/3)+1/2*(-2/3)
=â15/6-1/3
=(â15-2)/6
cos(Ï/3-α)
=cos(Ï/3)cosα+sin(Ï/3)sinα
=1/2*(â5/3)+â3/2*(-2/3)
=â5/6-â3/3
=(â5-2â3)/6
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