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(* Formalization of the Chou, Gao and Zhang's decision procedure.          *)
(* Julien Narboux (Julien@narboux.fr)                                      *)
(* LIX/INRIA FUTURS 2004-2006                                              *)
(* University of Strasbourg 2008                                           *)
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Require Export field_variable_isolation_tactic.
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(*  General properties about fields                    *)
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Proof with try solve [ ring | congruence ].
intros...
assert (a + b - a = a - a)...
assert (a - a = 0)...
rewrite H1 in H0...
assert (a + b - a = b)...
Qed.
intros.
rewrite H.
ring.
Qed.
Proof with try solve [ ring | congruence ].
intros...
assert (a + - a = a + 0)...
assert (a + - a = 0)...
rewrite H1 in H0...
assert (a + 0 = a)...
Qed.

Lemma field_prop_5 : forall a b : F, - a = - b -> a = b.