{% f(x,y) \approx f(x_0, y_0) + \frac{\partial f}{\partial x} (x-x_0) + \frac{\partial f}{\partial y} (y-y_0) + %} {% \frac{1}{2 !} \frac{\partial^2 f}{\partial x ^2} (x-x_0)^2 + \frac{1}{2 !} \frac{\partial^2 f}{\partial y ^2} (y-y_0)^2 + \frac{1}{2 !} \frac{\partial^2 f}{\partial x \partial y} (x-x_0)(y-y_0) + ... %}