xy'+xcos(y/x)-y+x=0y'+cos(y/x)-y/x+1=0令u=y/xu'x+u+cos(u)-u+1=0u'x+cos(u)+1=0du/(1+cos(u))=-dx/x令u1=tan(u/2)有du1=-dx/xu1=-ln(x)+C1tan(u/2)=-ln(x)+C1x=C*exp(-tan(y/(2x)))