Z'x=2xsin(y²)+2ysinxsiny+2xycosxsinyZ'y=x²*cos(y²)*2y+2xsinxsiny+2xysinxcosy+2y故sz=Z'xdx+Z'ydy=[2xsin(y²)+2ysinxsiny+2xycosxsiny]dx+[2yx²cos(y²)+2xsinxsiny+2xysinxcosy+2y]dy
