已知cos(π/6-α)=1/3,求cos(5π/6+α)sin(2π/3-α)的值

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cos(5π/6+α)sin(2π/3-α)
=-cos(π-5π/6-α)sin(π/2+π/6-α)
=-cos(π/6-α)cos(π/6-α)
=-1/3*1/3
=-1/9

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