reserve n for Nat,
  i for Integer,
  p, x, x0, y for Real,
  q for Rational,
  f for PartFunc of REAL,REAL;

theorem Th14:
  y > 0 implies exp_R(log(number_e,y)) = y
proof
  assume y > 0;
  then number_e to_power log(number_e,y) = y by Lm4,POWER:def 3;
  hence thesis by Th9;
end;
