求f(x,y)=sin(xy+x+y)的全微分?

问题描述:

求f(x,y)=sin(xy+x+y)的全微分?

f'x=cos(xy+x+y)*(y+1)
f'y=cos(xy+x+y)*(x+1)
dz=f'xdx+f'ydy=cos(xy+x+y)*[(y+1)dx+(x+1)dy]