设x=(x+sinx)y2，求dz．
∂z/∂x=y2(x+sinx)y2-1(1+cosx)，∂z/∂y=2y(x+sinx)y2ln(x+sinx)，dz=y(x+sinx)y2-1[y(1+cosx)dx+2(x+sinx)In(x+sinx)dy]．
设x=(x+sinx)y2，求dz．
∂z/∂x=y2(x+sinx)y2-1(1+cosx)，∂z/∂y=2y(x+sinx)y2ln(x+sinx)，dz=y(x+sinx)y2-1[y(1+cosx)dx+2(x+sinx)In(x+sinx)dy]．
