
设∂为锐角,若cos(∂+π/6)=4/5,则sin(π/3-∂)=
设∂为锐角,若cos(∂+π/6)=4/5,则sin(π/3-∂)=帮忙看看这几道题怎么做谢谢...
设∂为锐角,若cos(∂+π/6)=4/5,则sin(π/3-∂)=帮忙看看这几道题怎么做谢谢
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4、原式=2[(1/2)sinx - (√3/2)cosx]
=2sin(x - π/3)
∵0≤x≤2π
∴-π/3≤x - π/3≤5π/3
则x - π/3=π/2
∴x=5π/6
=2sin(x - π/3)
∵0≤x≤2π
∴-π/3≤x - π/3≤5π/3
则x - π/3=π/2
∴x=5π/6
追答
3、sin(π/3 - α)=sin(π/2 - π/6 - α)
=sin[π/2 - (α + π/6)]
=cos(α + π/6)
=4/5
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