设二元函数z=sin(x-y),求αz/αy,αy/αz,dz
问题描述：
设二元函数z=sin(x-y),求αz/αy,αy/αz,dz
答
题目有点错吧，应该是：
αz/αy=-cos(x-y)
αz/αx=cos(x-y)
dz=cos(x-y)dx-cos(x-y)dy
答
dz/dy=-cos(x-y)
dy/dz=-1/cos(x-y)
dz/dx=cos(x-y)
dz=cos(x-y)dx-cos(x-y)dy
答
∂z/∂x=cos(x-y)
∂z/∂y=-cos(x-y)
dz=∂z/∂x*dx+∂z/∂y*dy
=cos(x-y)dx-cos(x-y)dy