theorem
  m <> 0 implies
  denominator(i/m) = m / ( i gcd m ) &
  numerator(i/m) = i / ( i gcd m )
  proof
    assume
A1: m <> 0;
    hence denominator(i/m) = m div ( i gcd m ) by Th15
    .= m / ( i gcd m ) by Th8;
    thus numerator(i/m) = i div ( i gcd m ) by A1,Th15
    .= i / ( i gcd m ) by Th7;
  end;
