definition subset_ext_f1 (A1) (A0) (f:A1âA0): đ«âšA1â© â đ«âšA0â© â
λu1,a0. ââa1. a1 Ï” u1 & f a1 = a0.
+definition subset_ext_f1_1 (A11) (A21) (A0) (f1:A11âA0) (f2:A21âA0): đ«âšA11â© â đ«âšA21â© â đ«âšA0â© â
+ λu11,u21,a0.
+ âšâš subset_ext_f1 A11 A0 f1 u11 a0
+ | subset_ext_f1 A21 A0 f2 u21 a0.
+
definition subset_ext_p1 (A1) (Q:predicate A1): predicate (đ«âšA1â©) â
λu1. âa1. a1 Ï” u1 â Q a1.
a1 Ï” u1 â f a1 Ï” subset_ext_f1 A1 A0 f u1.
/2 width=3 by ex2_intro/ qed.
+lemma subset_in_ext_f1_1_dx_1 (A11) (A21) (A0) (f1) (f2) (u11) (u21) (a11):
+ a11 Ï” u11 â f1 a11 Ï” subset_ext_f1_1 A11 A21 A0 f1 f2 u11 u21.
+/3 width=3 by subset_in_ext_f1_dx, or_introl/ qed.
+
+lemma subset_in_ext_f1_1_dx_2 (A11) (A21) (A0) (f1) (f2) (u11) (u21) (a21):
+ a21 Ï” u21 â f2 a21 Ï” subset_ext_f1_1 A11 A21 A0 f1 f2 u11 u21.
+/3 width=3 by subset_in_ext_f1_dx, or_intror/ qed.
+
(* Basic inversions *********************************************************)
lemma subset_in_inv_ext_p1_dx (A1) (Q) (u1) (a1):
/3 width=3 by subset_inclusion_ext_f1_bi, conj/
qed.
+lemma subset_equivalence_ext_f1_1_bi (A11) (A21) (A0) (f1) (f2) (u11) (u21) (v11) (v21):
+ u11 â v11 â u21 â v21 â
+ subset_ext_f1_1 A11 A21 A0 f1 f2 u11 u21 â subset_ext_f1_1 A11 A21 A0 f1 f2 v11 v21.
+#A11 #A21 #A0 #f1 #f2 #u11 #u21 #v11 #v21 * #Huv11 #Hvu11 * #Huv21 #Hvu21
+/3 width=5 by subset_inclusion_ext_f1_1_bi, conj/
+qed.
+
lemma subset_inclusion_ext_f1_compose (A0) (A1) (A2) (f1) (f2) (u):
subset_ext_f1 A1 A2 f2 (subset_ext_f1 A0 A1 f1 u) â subset_ext_f1 A0 A2 (f2âf1) u.
/3 width=1 by subset_inclusion_ext_f1_compose_dx, subset_inclusion_ext_f1_compose_sn, conj/
/3 width=1 by subset_in_ext_f1_dx/
qed.
+lemma subset_inclusion_ext_f1_1_bi (A11) (A21) (A0) (f1) (f2) (u11) (u21) (v11) (v21):
+ u11 â v11 â u21 â v21 â
+ subset_ext_f1_1 A11 A21 A0 f1 f2 u11 u21 â subset_ext_f1_1 A11 A21 A0 f1 f2 v11 v21.
+#A11 #A21 #A0 #f1 #f2 #u11 #u21 #v11 #v21 #Huv11 #Huv21 #a0 *
+/3 width=3 by subset_inclusion_ext_f1_bi, or_introl, or_intror/
+qed.
+
lemma subset_inclusion_ext_p1_trans (A1) (Q) (u1) (v1):
u1 â v1 â subset_ext_p1 A1 Q v1 â subset_ext_p1 A1 Q u1.
#A1 #Q #u1 #v1 #Huv1 #Hv1