已知Sin(π/6-α)=1/3,则Cos(2π/3+2α)=?本人智商不高,

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已知Sin(π/6-α)=1/3,则Cos(2π/3+2α)=?本人智商不高,已知Sin(π/6-α)=1/3,则Cos(2π/3+2α)=?本人智商不高,已知Sin(π/6-α)=1/3,则Cos(

已知Sin(π/6-α)=1/3,则Cos(2π/3+2α)=?本人智商不高,
已知Sin(π/6-α)=1/3,则Cos(2π/3+2α)=?
本人智商不高,

已知Sin(π/6-α)=1/3,则Cos(2π/3+2α)=?本人智商不高,
cos(2π/3+2α)
=-cos[π-(2π/3+2α)]
=-cos(π/3-2α)
=-cos[2(π/6-α)]
=-{1-2[sin(π/6-α)]^2}
=-(1-2/9)
=-7/9