(sinydx+xcosydy)+(y^2sinxdx-2ycosx)dy=0
[sinydx+xd(siny)]+[y^2d(-cosx)-cosx(dy^2)]=0
d(xsiny)+d(-y^2cosx)=0
d(xsiny-y^2cosx)=0
xsiny-y^2cosx=C,C为任意常数.
(sinydx+xcosydy)+(y^2sinxdx-2ycosx)dy=0
[sinydx+xd(siny)]+[y^2d(-cosx)-cosx(dy^2)]=0
d(xsiny)+d(-y^2cosx)=0
d(xsiny-y^2cosx)=0
xsiny-y^2cosx=C,C为任意常数.