Section 14.4: Tangent Planes
Differentials
If \(z = f(x,y)\), its differential is defined as
\[ dz = f_x(x, y)\,dx + f_y(x, y)\,dy = \frac{\partial z}{\partial x} dx + \frac{\partial z}{\partial y} dy \]
If \(z = f(x,y)\), its differential is defined as
\[ dz = f_x(x, y)\,dx + f_y(x, y)\,dy = \frac{\partial z}{\partial x} dx + \frac{\partial z}{\partial y} dy \]