intros a b; case a; case b; simpl in |- *; auto.
intros a0 m a1 m0 H'; elim H'; intros H'0 H'1; rewrite H'1; clear H'.
split; auto.
apply (eqA_trans _ _ _ _ _ _ _ _ _ cs) with (y := multA a0 A1); auto.
apply (eqA_trans _ _ _ _ _ _ _ _ _ cs) with (y := multA A1 a0); auto.
apply (eqA_sym _ _ _ _ _ _ _ _ _ cs); apply multA_A1_l with (1 := cs); auto.
apply (eqA_sym _ _ _ _ _ _ _ _ _ cs); auto.
apply sym_eq; unfold M1 in |- *; apply mult_mon_zero_r.
Qed.

Theorem nZero_invTerm_T1 : ~ zeroP (invTerm T1).
apply nZero_invTerm_nZero; auto.