z=u^2v-uv^2,u=xcosy,v=xsiny,求az/ax

z=e^usinv=e^(xsiny)sin(xcosy)
∂z/∂x=e^(xsiny)[(siny)]sin(xcosy)-e^(xsiny)cos(xcosy)[(cosy)
=e^(xsiny)[siny)sin(xcosy)-cos(xcosy)(cosy)]
同理可得：
∂z/∂y=.

z=e^xcosy+sin(xy)
dz= e^x.sinydy + cosy.e^x dx +(xdy + ydx)cos(xy)