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 Th20:
  n>=1 implies n -Root 1 = 1
proof
A1: 1 |^ n = 1;
  assume n>=1;
  hence thesis by A1,Def2;
end;
