化简sin(啊尔法+贝塔)cos啊尔法-1/2[sin(2啊尔法+贝塔)-sin贝塔]

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解由sin（α+β）cosα-1/2[sin（2α+β）誉肆-sinβ]
=sin（α+β）cosα-1/2[sin（α+β+α）-sinβ]
=sin（α+β）cosα-1/2[sin（锋贺α+β+α）-sinβ]
=sin（α+β）cosα-1/2[sin（α+β）cosα+cos（α+β）银虚派sinα-sinβ]
=sin（α+β）cosα-1/2sin（α+β）cosα-1/2cos（α+β）sinα+1/2sinβ
=1/2sin（α+β）cosα-1/2cos（α+β）sinα+1/2sinβ
=1/2[sin（α+β）cosα-cos（α+β）sinα]+1/2sinβ
=1/2sin（α+β-β）+1/2sinβ
=1/2sin（α）+1/2sinβ

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