z=arctanx+y/1-xy 的偏导数和全微分

z=(arctan(x+y)]/(x-y) ∂z/∂x={1/√[1+(x+y)²] -arctan(x+y)}/(x-y)² ∂z/∂y=-{1/√[1+(x+y)²]+arctan(x+y)}/(x-y)² =>dz={{1/√[1+(x+y)²] -arctan(x+y)}/(x-y)²}dx-{{