cosxcosy+sinxsiny=1/2,sin2x+sin2y=2/3,则sin(x+y)等于多少

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cosxcosy+sinxsiny=1/2,sin2x+sin2y=2/3,则sin(x+y)等于多少
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cosxcosy+sinxsiny=1/2,sin2x+sin2y=2/3,则sin(x+y)等于多少
cosxcosy+sinxsiny=1/2,sin2x+sin2y=2/3,则sin(x+y)等于多少

cosxcosy+sinxsiny=1/2,sin2x+sin2y=2/3,则sin(x+y)等于多少
cosxcosy+sinxsiny=1/2
cos(x-y)=1/2
sin2x+sin2y=2/3
sin2x+sin2y=2sin(x+y)cos(x-y)=2/3
sin(x+y)=1/[3cos(x-y)]=1/[3*(1/2)]=2/3
sin(x+y)=2/3

因为cosxcosy+sinxsiny=1/2所以cos(x-y)=1/2
再和差化积sin2x+sin2y=2sin(x+y)cos(x-y)=2/3
所以sin(x+y)=2/3