reserve x for set;
reserve a, b, c for Real;
reserve m, n, m1, m2 for Nat;
reserve k, l for Integer;
reserve p, q for Rational;
reserve s1, s2 for Real_Sequence;

theorem Th81:
  a > 0 implies a #R b > 0
proof
  assume
A1: a > 0;
  then a #R b <> 0 by Lm9;
  hence thesis by A1,Lm8;
end;
