Gauss’s lemma Let be an odd prime, be an integer coprime to . Take the least residues of , i.e. reduce them to integers
in
. Let be the number of
members in this set that are greater than . Then
Proof. Q has exactly elements since and is a prime.We can rewrite Q to integers in by rewriting all into .
Corollary Let p be an odd prime. Then
Proof. Because , we only need to find out
the cut-off
point