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