
theorem FR3:
  for a be Real, b be Integer holds frac (a*b) = frac (b*frac a)
  proof
    let a be Real, b be Integer;
    frac (a*b) = frac (([\a/]*frac b) + ([\b/]*frac a) + (frac a)*(frac b))
      by FR2;
    hence thesis;
  end;
