intros a b nZa nZb nZppab p.
apply
(eqTerm_trans _ _ _ _ _ _ _ _ _ cs n)
with (y := multTerm (A:=A) multA (n:=n) (divTerm a nZa) b);
auto.
apply
(eqTerm_trans _ _ _ _ _ _ _ _ _ cs n)
with (y := divTerm (multTerm (A:=A) multA (n:=n) a b) nZa);
auto.
apply (eqTerm_sym _ _ _ _ _ _ _ _ _ cs n); auto.
Qed.

Theorem divP_comp_ppc1 :
forall (a b : Term A n) (nZa : ~ zeroP (A:=A) A0 eqA (n:=n) a)
(nZb : ~ zeroP (A:=A) A0 eqA (n:=n) b)
(nZppab : ~ zeroP (A:=A) A0 eqA (n:=n) (ppc a b))
(p : list (Term A n)),
eqTerm (A:=A) eqA (n:=n) a
(multTerm (A:=A) multA (n:=n)
(divTerm (multTerm (A:=A) multA (n:=n) a b) nZppab)
(divTerm (ppc a b) nZb)).