let a be Real; :: thesis: {a} is Element of Borel_Sets

{a} = [.a,a.] by XXREAL_1:17;

hence {a} is Element of Borel_Sets by MEASUR10:5; :: thesis: verum

{a} = [.a,a.] by XXREAL_1:17;

hence {a} is Element of Borel_Sets by MEASUR10:5; :: thesis: verum