proposition: Lemma open_subspaceTI (U : set (subspace A)) : open (A `&` U : set (subspace A)) = open U.
proof: Proof. by rewrite setIC open_subspaceIT. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed