Theorem indexfi 9127

Description: If for every element of a finite indexing set 𝐴 there exists a corresponding element of another set 𝐵, then there exists a finite subset of 𝐵 consisting only of those elements which are indexed by 𝐴. Proven without the Axiom of Choice, unlike indexdom 35892. (Contributed by Jeff Madsen, 2-Sep-2009.) (Proof shortened by Mario Carneiro, 12-Sep-2015.)

Assertion

Ref	Expression
indexfi	⊢ ((𝐴 ∈ Fin ∧ 𝐵 ∈ 𝑀 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) → ∃𝑐 ∈ Fin (𝑐 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝑐 𝜑 ∧ ∀𝑦 ∈ 𝑐 ∃𝑥 ∈ 𝐴 𝜑))

Distinct variable groups:   𝑥,𝑐,𝑦,𝐴   𝐵,𝑐,𝑥,𝑦   𝜑,𝑐

Allowed substitution hints:   𝜑(𝑥,𝑦)   𝑀(𝑥,𝑦,𝑐)

Proof of Theorem indexfi

Dummy variables 𝑓 𝑤 𝑧 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		nfv 1917	. . . . . 6 ⊢ Ⅎ𝑧𝜑
2		nfsbc1v 3736	. . . . . 6 ⊢ Ⅎ𝑦[𝑧 / 𝑦]𝜑
3		sbceq1a 3727	. . . . . 6 ⊢ (𝑦 = 𝑧 → (𝜑 ↔ [𝑧 / 𝑦]𝜑))
4	1, 2, 3	cbvrexw 3374	. . . . 5 ⊢ (∃𝑦 ∈ 𝐵 𝜑 ↔ ∃𝑧 ∈ 𝐵 [𝑧 / 𝑦]𝜑)
5	4	ralbii 3092	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑 ↔ ∀𝑥 ∈ 𝐴 ∃𝑧 ∈ 𝐵 [𝑧 / 𝑦]𝜑)
6		dfsbcq 3718	. . . . 5 ⊢ (𝑧 = (𝑓‘𝑥) → ([𝑧 / 𝑦]𝜑 ↔ [(𝑓‘𝑥) / 𝑦]𝜑))
7	6	ac6sfi 9058	. . . 4 ⊢ ((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑧 ∈ 𝐵 [𝑧 / 𝑦]𝜑) → ∃𝑓(𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑))
8	5, 7	sylan2b 594	. . 3 ⊢ ((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) → ∃𝑓(𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑))
9		simpll 764	. . . . 5 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → 𝐴 ∈ Fin)
10		ffn 6600	. . . . . . 7 ⊢ (𝑓:𝐴⟶𝐵 → 𝑓 Fn 𝐴)
11	10	ad2antrl 725	. . . . . 6 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → 𝑓 Fn 𝐴)
12		dffn4 6694	. . . . . 6 ⊢ (𝑓 Fn 𝐴 ↔ 𝑓:𝐴–onto→ran 𝑓)
13	11, 12	sylib 217	. . . . 5 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → 𝑓:𝐴–onto→ran 𝑓)
14		fofi 9105	. . . . 5 ⊢ ((𝐴 ∈ Fin ∧ 𝑓:𝐴–onto→ran 𝑓) → ran 𝑓 ∈ Fin)
15	9, 13, 14	syl2anc 584	. . . 4 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ran 𝑓 ∈ Fin)
16		frn 6607	. . . . 5 ⊢ (𝑓:𝐴⟶𝐵 → ran 𝑓 ⊆ 𝐵)
17	16	ad2antrl 725	. . . 4 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ran 𝑓 ⊆ 𝐵)
18		fnfvelrn 6958	. . . . . . . . 9 ⊢ ((𝑓 Fn 𝐴 ∧ 𝑥 ∈ 𝐴) → (𝑓‘𝑥) ∈ ran 𝑓)
19	10, 18	sylan 580	. . . . . . . 8 ⊢ ((𝑓:𝐴⟶𝐵 ∧ 𝑥 ∈ 𝐴) → (𝑓‘𝑥) ∈ ran 𝑓)
20		rspesbca 3814	. . . . . . . . 9 ⊢ (((𝑓‘𝑥) ∈ ran 𝑓 ∧ [(𝑓‘𝑥) / 𝑦]𝜑) → ∃𝑦 ∈ ran 𝑓𝜑)
21	20	ex 413	. . . . . . . 8 ⊢ ((𝑓‘𝑥) ∈ ran 𝑓 → ([(𝑓‘𝑥) / 𝑦]𝜑 → ∃𝑦 ∈ ran 𝑓𝜑))
22	19, 21	syl 17	. . . . . . 7 ⊢ ((𝑓:𝐴⟶𝐵 ∧ 𝑥 ∈ 𝐴) → ([(𝑓‘𝑥) / 𝑦]𝜑 → ∃𝑦 ∈ ran 𝑓𝜑))
23	22	ralimdva 3108	. . . . . 6 ⊢ (𝑓:𝐴⟶𝐵 → (∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑 → ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ran 𝑓𝜑))
24	23	imp 407	. . . . 5 ⊢ ((𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑) → ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ran 𝑓𝜑)
25	24	adantl 482	. . . 4 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ran 𝑓𝜑)
26		simpr 485	. . . . . . . 8 ⊢ ((((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) ∧ 𝑤 ∈ 𝐴) → 𝑤 ∈ 𝐴)
27		simprr 770	. . . . . . . . . 10 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)
28		nfv 1917	. . . . . . . . . . 11 ⊢ Ⅎ𝑤[(𝑓‘𝑥) / 𝑦]𝜑
29		nfsbc1v 3736	. . . . . . . . . . 11 ⊢ Ⅎ𝑥[𝑤 / 𝑥][(𝑓‘𝑤) / 𝑦]𝜑
30		fveq2 6774	. . . . . . . . . . . . 13 ⊢ (𝑥 = 𝑤 → (𝑓‘𝑥) = (𝑓‘𝑤))
31	30	sbceq1d 3721	. . . . . . . . . . . 12 ⊢ (𝑥 = 𝑤 → ([(𝑓‘𝑥) / 𝑦]𝜑 ↔ [(𝑓‘𝑤) / 𝑦]𝜑))
32		sbceq1a 3727	. . . . . . . . . . . 12 ⊢ (𝑥 = 𝑤 → ([(𝑓‘𝑤) / 𝑦]𝜑 ↔ [𝑤 / 𝑥][(𝑓‘𝑤) / 𝑦]𝜑))
33	31, 32	bitrd 278	. . . . . . . . . . 11 ⊢ (𝑥 = 𝑤 → ([(𝑓‘𝑥) / 𝑦]𝜑 ↔ [𝑤 / 𝑥][(𝑓‘𝑤) / 𝑦]𝜑))
34	28, 29, 33	cbvralw 3373	. . . . . . . . . 10 ⊢ (∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑 ↔ ∀𝑤 ∈ 𝐴 [𝑤 / 𝑥][(𝑓‘𝑤) / 𝑦]𝜑)
35	27, 34	sylib 217	. . . . . . . . 9 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ∀𝑤 ∈ 𝐴 [𝑤 / 𝑥][(𝑓‘𝑤) / 𝑦]𝜑)
36	35	r19.21bi 3134	. . . . . . . 8 ⊢ ((((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) ∧ 𝑤 ∈ 𝐴) → [𝑤 / 𝑥][(𝑓‘𝑤) / 𝑦]𝜑)
37		rspesbca 3814	. . . . . . . 8 ⊢ ((𝑤 ∈ 𝐴 ∧ [𝑤 / 𝑥][(𝑓‘𝑤) / 𝑦]𝜑) → ∃𝑥 ∈ 𝐴 [(𝑓‘𝑤) / 𝑦]𝜑)
38	26, 36, 37	syl2anc 584	. . . . . . 7 ⊢ ((((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) ∧ 𝑤 ∈ 𝐴) → ∃𝑥 ∈ 𝐴 [(𝑓‘𝑤) / 𝑦]𝜑)
39	38	ralrimiva 3103	. . . . . 6 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ∀𝑤 ∈ 𝐴 ∃𝑥 ∈ 𝐴 [(𝑓‘𝑤) / 𝑦]𝜑)
40		dfsbcq 3718	. . . . . . . . 9 ⊢ (𝑧 = (𝑓‘𝑤) → ([𝑧 / 𝑦]𝜑 ↔ [(𝑓‘𝑤) / 𝑦]𝜑))
41	40	rexbidv 3226	. . . . . . . 8 ⊢ (𝑧 = (𝑓‘𝑤) → (∃𝑥 ∈ 𝐴 [𝑧 / 𝑦]𝜑 ↔ ∃𝑥 ∈ 𝐴 [(𝑓‘𝑤) / 𝑦]𝜑))
42	41	ralrn 6964	. . . . . . 7 ⊢ (𝑓 Fn 𝐴 → (∀𝑧 ∈ ran 𝑓∃𝑥 ∈ 𝐴 [𝑧 / 𝑦]𝜑 ↔ ∀𝑤 ∈ 𝐴 ∃𝑥 ∈ 𝐴 [(𝑓‘𝑤) / 𝑦]𝜑))
43	11, 42	syl 17	. . . . . 6 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → (∀𝑧 ∈ ran 𝑓∃𝑥 ∈ 𝐴 [𝑧 / 𝑦]𝜑 ↔ ∀𝑤 ∈ 𝐴 ∃𝑥 ∈ 𝐴 [(𝑓‘𝑤) / 𝑦]𝜑))
44	39, 43	mpbird 256	. . . . 5 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ∀𝑧 ∈ ran 𝑓∃𝑥 ∈ 𝐴 [𝑧 / 𝑦]𝜑)
45		nfv 1917	. . . . . 6 ⊢ Ⅎ𝑧∃𝑥 ∈ 𝐴 𝜑
46		nfcv 2907	. . . . . . 7 ⊢ Ⅎ𝑦𝐴
47	46, 2	nfrex 3242	. . . . . 6 ⊢ Ⅎ𝑦∃𝑥 ∈ 𝐴 [𝑧 / 𝑦]𝜑
48	3	rexbidv 3226	. . . . . 6 ⊢ (𝑦 = 𝑧 → (∃𝑥 ∈ 𝐴 𝜑 ↔ ∃𝑥 ∈ 𝐴 [𝑧 / 𝑦]𝜑))
49	45, 47, 48	cbvralw 3373	. . . . 5 ⊢ (∀𝑦 ∈ ran 𝑓∃𝑥 ∈ 𝐴 𝜑 ↔ ∀𝑧 ∈ ran 𝑓∃𝑥 ∈ 𝐴 [𝑧 / 𝑦]𝜑)
50	44, 49	sylibr 233	. . . 4 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ∀𝑦 ∈ ran 𝑓∃𝑥 ∈ 𝐴 𝜑)
51		sseq1 3946	. . . . . 6 ⊢ (𝑐 = ran 𝑓 → (𝑐 ⊆ 𝐵 ↔ ran 𝑓 ⊆ 𝐵))
52		rexeq 3343	. . . . . . 7 ⊢ (𝑐 = ran 𝑓 → (∃𝑦 ∈ 𝑐 𝜑 ↔ ∃𝑦 ∈ ran 𝑓𝜑))
53	52	ralbidv 3112	. . . . . 6 ⊢ (𝑐 = ran 𝑓 → (∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝑐 𝜑 ↔ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ran 𝑓𝜑))
54		raleq 3342	. . . . . 6 ⊢ (𝑐 = ran 𝑓 → (∀𝑦 ∈ 𝑐 ∃𝑥 ∈ 𝐴 𝜑 ↔ ∀𝑦 ∈ ran 𝑓∃𝑥 ∈ 𝐴 𝜑))
55	51, 53, 54	3anbi123d 1435	. . . . 5 ⊢ (𝑐 = ran 𝑓 → ((𝑐 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝑐 𝜑 ∧ ∀𝑦 ∈ 𝑐 ∃𝑥 ∈ 𝐴 𝜑) ↔ (ran 𝑓 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ran 𝑓𝜑 ∧ ∀𝑦 ∈ ran 𝑓∃𝑥 ∈ 𝐴 𝜑)))
56	55	rspcev 3561	. . . 4 ⊢ ((ran 𝑓 ∈ Fin ∧ (ran 𝑓 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ran 𝑓𝜑 ∧ ∀𝑦 ∈ ran 𝑓∃𝑥 ∈ 𝐴 𝜑)) → ∃𝑐 ∈ Fin (𝑐 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝑐 𝜑 ∧ ∀𝑦 ∈ 𝑐 ∃𝑥 ∈ 𝐴 𝜑))
57	15, 17, 25, 50, 56	syl13anc 1371	. . 3 ⊢ (((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) ∧ (𝑓:𝐴⟶𝐵 ∧ ∀𝑥 ∈ 𝐴 [(𝑓‘𝑥) / 𝑦]𝜑)) → ∃𝑐 ∈ Fin (𝑐 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝑐 𝜑 ∧ ∀𝑦 ∈ 𝑐 ∃𝑥 ∈ 𝐴 𝜑))
58	8, 57	exlimddv 1938	. 2 ⊢ ((𝐴 ∈ Fin ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) → ∃𝑐 ∈ Fin (𝑐 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝑐 𝜑 ∧ ∀𝑦 ∈ 𝑐 ∃𝑥 ∈ 𝐴 𝜑))
59	58	3adant2 1130	1 ⊢ ((𝐴 ∈ Fin ∧ 𝐵 ∈ 𝑀 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝜑) → ∃𝑐 ∈ Fin (𝑐 ⊆ 𝐵 ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝑐 𝜑 ∧ ∀𝑦 ∈ 𝑐 ∃𝑥 ∈ 𝐴 𝜑))

Syntax hints:   → wi 4   ↔ wb 205   ∧ wa 396   ∧ w3a 1086   = wceq 1539  ∃wex 1782   ∈ wcel 2106  ∀wral 3064  ∃wrex 3065  [wsbc 3716   ⊆ wss 3887  ran crn 5590   Fn wfn 6428  ⟶wf 6429  –onto→wfo 6431  ‘cfv 6433  Fincfn 8733

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1913  ax-6 1971  ax-7 2011  ax-8 2108  ax-9 2116  ax-10 2137  ax-11 2154  ax-12 2171  ax-ext 2709  ax-sep 5223  ax-nul 5230  ax-pow 5288  ax-pr 5352  ax-un 7588

This theorem depends on definitions:  df-bi 206  df-an 397  df-or 845  df-3or 1087  df-3an 1088  df-tru 1542  df-fal 1552  df-ex 1783  df-nf 1787  df-sb 2068  df-mo 2540  df-eu 2569  df-clab 2716  df-cleq 2730  df-clel 2816  df-nfc 2889  df-ne 2944  df-ral 3069  df-rex 3070  df-reu 3072  df-rab 3073  df-v 3434  df-sbc 3717  df-dif 3890  df-un 3892  df-in 3894  df-ss 3904  df-pss 3906  df-nul 4257  df-if 4460  df-pw 4535  df-sn 4562  df-pr 4564  df-op 4568  df-uni 4840  df-br 5075  df-opab 5137  df-mpt 5158  df-tr 5192  df-id 5489  df-eprel 5495  df-po 5503  df-so 5504  df-fr 5544  df-we 5546  df-xp 5595  df-rel 5596  df-cnv 5597  df-co 5598  df-dm 5599  df-rn 5600  df-res 5601  df-ima 5602  df-ord 6269  df-on 6270  df-lim 6271  df-suc 6272  df-iota 6391  df-fun 6435  df-fn 6436  df-f 6437  df-f1 6438  df-fo 6439  df-f1o 6440  df-fv 6441  df-om 7713  df-1o 8297  df-er 8498  df-en 8734  df-dom 8735  df-fin 8737

This theorem is referenced by:  filbcmb  35898