\[ y = h(x), \quad \dot{y} = \frac{\partial h}{\partial x} f(x) + \frac{\partial h}{\partial x} g(x) u \] \[ u = \left( \frac{\partial h}{\partial x} g(x) \right)^{-1} \left( v - \frac{\partial h}{\partial x} f(x) \right) \]