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 Th5:
  n>1 & i,n are_coprime implies i <> 0
proof
  assume A1:n>1 & i,n are_coprime;
  assume i = 0;
  then i gcd n > 1 by A1,NEWTON:52;
  hence contradiction by A1,INT_2:def 3;
end;
