reserve x for set;
reserve a, b, c, d, e for Real;
reserve m, n, m1, m2 for Nat;
reserve k, l for Integer;
reserve p for Rational;

theorem
  n is odd implies n-root (-1) = -1
proof
  assume
A1: n is odd;
   then
A2: n>=1 by ABIAN:12;
  thus
  n-root (-1) = - n -Root (-(-1)) by A1,Def1
    .= - 1 by A2,PREPOWER:20;
end;
