3sinx+4cosy=5,平方 9sin^2x+24sinxcosy+16cos^2y=25
3cosx+4siny=-2,平方 9cos^2x+24cosxsiny+16sin^2y=4
相加
9+24（sinxcosy+cosxsiny）+16=29
sinxcosy+cosxsiny=1/6
sin(x+y)= 1/6
3sinx+4cosy=5,3cosx+4siny=-2,则sin(x+y)=
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