Reconstructing a Function from its Gradient
Differentials We begin by reviewing the one-variable case. If f is differentiable at x, then for small h, the increment Δf = f (x + h) − f (x) can be approximated by the differential d f = f´(x) h.
Differentials
Differentials is called the increment of f , and the dot product is called the differential (more formally, the total differential).
Differentials As in the one-variable case, for small h, the differential and the increment are approximately equal:
Differentials
Example
Theorem
Examples