
theorem Th6:
  for x,y being Element of REAL+ st x - y = {} holds x = y
proof
  let x,y be Element of REAL+;
  assume
A1: x - y = {};
  0 <> [{},y -' x];
  then y <=' x & x -' y = {} by A1,ARYTM_1:def 2;
  hence thesis by ARYTM_1:10;
end;
