对x求导(xy)'=x'*y+x*y'=y+x*y'[sin(x+y)]'=cos(x+y)*(x+y)'=(1+y')cos(x+y)=cos(x+y)+cos(x+y)*y'1'=0所以y+x*y'-cos(x+y)-cos(x+y)*y'=0y'=[y-cos(x+y)]/[cos(x+y)-x]