
theorem Th2:
  for x,y being ExtReal, a,b being Real st x = a & y = b
  holds x / y = a / b
  proof
    let x,y be ExtReal, a,b be Real such that
A1: x = a;
    assume y = b;
    then y" = b" by XXREAL_3:def 6;
    hence thesis by A1,XXREAL_3:def 5;
  end;
