cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)
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cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)
cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)
cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)
cosx-cosy=1/4 cos²x-2cosxcosy+cos²y=1/16
sinx-siny=1/3 sin²x-2sinxsiny+sin²y=1/9
两式相加
2-2cosxcosy-2sinxsiny=1/16+1/9
2-2cos(x-y)=25/144
2cos(x-y)=(288-25)/144
cos(x-y)=263/288
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cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)
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cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)=?
cosx-cosy=1/2,sinx-siny=1/3,sin(x+y)=RT