intros a1 H' b2 H'0 H'1;
apply (eqA_trans _ _ _ _ _ _ _ _ _ cs) with (y := multA a1 A0);
auto.
apply (eqA_trans _ _ _ _ _ _ _ _ _ cs) with (y := multA A0 a1); auto.
Qed.

Theorem multTerm_plusTerm_dist_l :
forall a b c : Term,
eqTerm (plusTerm (multTerm a c) (multTerm b c)) (multTerm (plusTerm a b) c).