proposition: Lemma openC (D : set T) : open (~`D) = closed (D).
proof: Proof. by rewrite -closedC setCK. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed