Section CPair_Order.
intros.
apply le_trans with (cPair (cPairPi1 a) (cPairPi2 a)).
apply cPairLe1.
rewrite cPairProjections.
apply le_n.
Qed.
intros.
apply le_trans with (cPair (cPairPi1 a) (cPairPi2 a)).
apply cPairLe2.
rewrite cPairProjections.
apply le_n.
Qed.

Lemma cPairLe3 :
forall a b c d : nat, a <= b -> c <= d -> cPair a c <= cPair b d.