fact: Definition derive1 V (f : R -> V) (a : R) := lim ((fun h => h^-1 *: (f (h + a) - f a)) @ 0^').
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrnum matrix interval) mathcomp(mathcomp_extra boolp classical_sets functions) reals signed topology prodnormedzmodule normedtype landau forms