# Differentiability

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Revision as of 20:35, 22 January 2019 by A WASSERMANN (talk | contribs)

If the function [math]f: D \to {\mathbb R}[/math] is differentiable in [math]x_0\in D[/math] then there is a function [math]f_1: D \to {\mathbb R}[/math] that is continuous in [math]x_0[/math] such that

- [math] f(x) = f(x_0) + (x-x_0) f_1(x) \,.[/math]