opp_inverse: left_inverse ? plus zero opp;
plus_strong_ext: ∀z.strong_ext ? (plus z)
}.
-
+
notation "0" with precedence 89 for @{ 'zero }.
interpretation "Abelian group zero" 'zero =
interpretation "Abelian group minus" 'minus a b =
(cic:/matita/groups/minus.con _ a b).
-
-lemma ap_rewl: ∀A:apartness.∀x,z,y:A. x ≈ y → y # z → x # z.
-intros (A x z y Exy Ayz); cases (ap_cotransitive ???x Ayz); [2:assumption]
-cases (Exy (ap_symmetric ??? a));
-qed.
-
-lemma ap_rewr: ∀A:apartness.∀x,z,y:A. x ≈ y → z # y → z # x.
-intros (A x z y Exy Azy); apply ap_symmetric; apply (ap_rewl ???? Exy);
-apply ap_symmetric; assumption;
-qed.
definition ext ≝ λA:apartness.λop:A→A. ∀x,y. x ≈ y → op x ≈ op y.
intros (G x y z Eyz); apply (strong_ext_to_ext ?? (plus_strong_ext ? x));
assumption;
qed.
+
+coercion cic:/matita/groups/feq_plusl.con.
lemma plus_strong_extr: ∀G:abelian_group.∀z:G.strong_ext ? (λx.x + z).
intros 5 (G z x y A); simplify in A;
assumption;
qed.
+coercion cic:/matita/groups/feq_plusr.con.
+
lemma fap_plusl: ∀G:abelian_group.∀x,y,z:G. y # z → x+y # x+z.
intros (G x y z Ayz); apply (plus_strong_ext ? (-x));
apply (ap_rewl ??? ((-x + x) + y));
|2: apply (ap_rewr ???? (zero_neutral ??)); assumption;]]]]
qed.
+
+
lemma fap_plusr: ∀G:abelian_group.∀x,y,z:G. y # z → y+x # z+x.
intros (G x y z Ayz); apply (plus_strong_extr ? (-x));
apply (ap_rewl ??? (y + (x + -x)));
theorem eq_opp_opp_x_x: ∀G:abelian_group.∀x:G.--x ≈ x.
intros (G x); apply (plus_cancl ??? (-x));
apply (eq_transitive ?? (--x + -x)); [apply plus_comm]
-apply (eq_transitive (carr G) (plus G (opp G (opp G x)) (opp G x)) (zero G) (plus G (opp G x) x) ? ?);
- [apply (opp_inverse G (opp G x)).
- |apply (eq_symmetric (carr G) (plus G (opp G x) x) (zero G) ?).
- apply (opp_inverse G x).
- ]
+apply (eq_transitive ?? 0); [apply opp_inverse]
+apply eq_symmetric; apply opp_inverse;
qed.
-theorem eq_zero_opp_zero: ∀G:abelian_group.0 ≈ -0.
- [ assumption
- | intros;
-apply (eq_transitive (carr G) (zero G) (plus G (opp G (zero G)) (zero G)) (opp G (zero G)) ? ?);
- [apply (eq_symmetric (carr G) (plus G (opp G (zero G)) (zero G)) (zero G) ?).
- apply (opp_inverse G (zero G)).
- |apply (eq_transitive (carr G) (plus G (opp G (zero G)) (zero G)) (plus G (zero G) (opp G (zero G))) (opp G (zero G)) ? ?);
- [apply (plus_comm G (opp G (zero G)) (zero G)).
- |apply (zero_neutral G (opp G (zero G))).
- ]
- ]]
+theorem eq_zero_opp_zero: ∀G:abelian_group.0 ≈ -0. [assumption]
+intro G; apply (plus_cancr ??? 0);
+apply (eq_transitive ?? 0); [apply zero_neutral;]
+apply eq_symmetric; apply opp_inverse;
qed.