reserve i,s,t,m,n,k for Nat,
        c,d,e for Element of NAT,
        fn for FinSequence of NAT,
        x,y for Integer;

theorem Th1:
  RelPrimes(m) c= Seg m
proof
  let x be object;
  assume x in RelPrimes(m);
  then ex k be Element of NAT st
    k = x & m,k are_coprime & k >= 1 & k <= m;
  hence x in Seg m;
end;
