proposition: Lemma cvgVP f a : a != 0 -> f\^-1 @ F --> a^-1 <-> f @ F --> a.
proof: Proof. move=> aN0; split=> /(cvgV _); last exact. by rewrite invrK invr_eq0 inv_funK; apply. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrint ssrnum finmap matrix) mathcomp(rat interval zmodp vector fieldext falgebra) mathcomp(mathcomp_extra boolp classical_sets functions) mathcomp(cardinality set_interval Rstruct) ereal reals signed topology prodnormedzmodule