求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2)
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求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2)求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2)求推导sinx-siny=2cos（(x+y)/
求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2)
求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2)
求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2)
用积化和差公式cosαsinβ= 1/2[sin(α+β)-sin(α-β)]
(x+y)/2=α (x-y)/2=β代入上式
得到2cos（(x+y)/2)sin((x-y)/2)=2*[1/2(sinx-siny)]=sinx-siny
sin((x+y)/2+(x-y)/2)-sin((x+y)/2-(x-y)/2)
化简出来就是了
cosαsinβ= 1/2[sin(α+β)-sin(α-β)]
(x+y)/2=α (x-y)/2=β
2cos（(x+y)/2)sin((x-y)/2)=2*[1/2(sinx-siny)]=sinx-siny
求推导sinx-siny=2cos（(x+y)/2)sin((x-y)/2)
两角和差公式sinx-siny=2sin[(x-y)/2]cos[(x+y)/2]推导.
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