 reserve n for Nat;
 reserve s1 for sequence of Euclid n,
         s2 for sequence of REAL-NS n;

theorem Th33:
  for I being non empty closed_interval Subset of REAL
  holds ex a,b being Real st a <= b & I = [.a,b.]
  proof
    let I be non empty closed_interval Subset of REAL;
    ex a,b be Real st I = [.a,b.] by MEASURE5:def 3;
    hence thesis by XXREAL_1:29;
  end;
