若sin(π/3-α)=1/3则cos(5π/6-α) 的值为若sin(π/3-α)=1/3则cos(5π/6-α)的值为

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若sin(π/3-α)=1/3则cos(5π/6-α) 的值为若sin(π/3-α)=1/3则cos(5π/6-α)的值为

若sin(π/3-α)=1/3则cos(5π/6-α) 的值为若sin(π/3-α)=1/3则cos(5π/6-α)的值为
若sin(π/3-α)=1/3则cos(5π/6-α) 的值为
若sin(π/3-α)=1/3则cos(5π/6-α)
的值为

若sin(π/3-α)=1/3则cos(5π/6-α) 的值为若sin(π/3-α)=1/3则cos(5π/6-α)的值为
【参考答案】
∵(5π/6) -a=(π/3) -a+(π/2)
∴cos(5π/6 -a)
=cos[(π/3 -a)+(π/2)]
=-sin[(π/3)-a]
=-1/3