reserve r for Real;

theorem Th26:
  for M being Reflexive Discerning non empty MetrStruct,
      a,b being Element of M holds 0 <= dist(a,b)
proof
  let M be Reflexive Discerning non empty MetrStruct;
  let a,b be Element of M;
  now
    per cases;
    suppose a = b;
      hence thesis by Th1;
    end;
    suppose a <> b;
      hence thesis by Th25;
    end;
  end;
  hence thesis;
end;
