Appendices

Abstract

To extend the concept of differentiability to a function of several variables, F : ℝⁿ→ℝ, at a point P0 of its domain, we must recall that the value of a differentiable function at a point close to P₀, P₀ + $\bar h$, can be approximated by the value of the function at the point, F(P0), plus the value of a linear transformation, called precisely the derivative at P₀, applied to the increment $\bar h$, where $\left\| {\bar h} \right\|$ is sufficiently small.