u=u(x,y,z)=xsin(2y)+y^(2z)+e^(xy)∂u/∂x=sin(2y)+ye^(xy)∂u/∂y=x+2zy^(2z-1)+xe^(xy)∂u/∂z=2 lny y^(2z)du=[sin(2y)+ye^(xy)]dx + [x+2zy^(2z-1)+xe^(xy)]dy + 2 lny y^(2z)dz