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Theorem fodomfir 9226
Description: There exists a mapping from a finite set onto any nonempty set that it dominates, proved without using the Axiom of Power Sets (unlike fodomr 9054). (Contributed by BTernaryTau, 23-Jun-2025.)
Assertion
Ref Expression
fodomfir ((𝐴 ∈ Fin ∧ ∅ ≺ 𝐵𝐵𝐴) → ∃𝑓 𝑓:𝐴onto𝐵)
Distinct variable groups:   𝐴,𝑓   𝐵,𝑓

Proof of Theorem fodomfir
Dummy variables 𝑔 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 relsdom 8888 . . . . . . 7 Rel ≺
21brrelex2i 5679 . . . . . 6 (∅ ≺ 𝐵𝐵 ∈ V)
3 0sdomg 9032 . . . . . . 7 (𝐵 ∈ V → (∅ ≺ 𝐵𝐵 ≠ ∅))
4 n0 4303 . . . . . . 7 (𝐵 ≠ ∅ ↔ ∃𝑧 𝑧𝐵)
53, 4bitrdi 287 . . . . . 6 (𝐵 ∈ V → (∅ ≺ 𝐵 ↔ ∃𝑧 𝑧𝐵))
62, 5syl 17 . . . . 5 (∅ ≺ 𝐵 → (∅ ≺ 𝐵 ↔ ∃𝑧 𝑧𝐵))
76ibi 267 . . . 4 (∅ ≺ 𝐵 → ∃𝑧 𝑧𝐵)
8 domfi 9111 . . . . . 6 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → 𝐵 ∈ Fin)
9 simpl 482 . . . . . 6 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → 𝐴 ∈ Fin)
10 brdomi 8894 . . . . . . . 8 (𝐵𝐴 → ∃𝑔 𝑔:𝐵1-1𝐴)
11 f1fn 6729 . . . . . . . . . . . 12 (𝑔:𝐵1-1𝐴𝑔 Fn 𝐵)
12 fnfi 9100 . . . . . . . . . . . 12 ((𝑔 Fn 𝐵𝐵 ∈ Fin) → 𝑔 ∈ Fin)
1311, 12sylan 580 . . . . . . . . . . 11 ((𝑔:𝐵1-1𝐴𝐵 ∈ Fin) → 𝑔 ∈ Fin)
1413ex 412 . . . . . . . . . 10 (𝑔:𝐵1-1𝐴 → (𝐵 ∈ Fin → 𝑔 ∈ Fin))
15 cnvfi 9098 . . . . . . . . . . . . . 14 (𝑔 ∈ Fin → 𝑔 ∈ Fin)
16 diffi 9097 . . . . . . . . . . . . . . 15 (𝐴 ∈ Fin → (𝐴 ∖ ran 𝑔) ∈ Fin)
17 snfi 8978 . . . . . . . . . . . . . . 15 {𝑧} ∈ Fin
18 xpfi 9218 . . . . . . . . . . . . . . 15 (((𝐴 ∖ ran 𝑔) ∈ Fin ∧ {𝑧} ∈ Fin) → ((𝐴 ∖ ran 𝑔) × {𝑧}) ∈ Fin)
1916, 17, 18sylancl 586 . . . . . . . . . . . . . 14 (𝐴 ∈ Fin → ((𝐴 ∖ ran 𝑔) × {𝑧}) ∈ Fin)
20 unfi 9093 . . . . . . . . . . . . . 14 ((𝑔 ∈ Fin ∧ ((𝐴 ∖ ran 𝑔) × {𝑧}) ∈ Fin) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∈ Fin)
2115, 19, 20syl2an 596 . . . . . . . . . . . . 13 ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∈ Fin)
22 df-f1 6495 . . . . . . . . . . . . . . . . . . 19 (𝑔:𝐵1-1𝐴 ↔ (𝑔:𝐵𝐴 ∧ Fun 𝑔))
2322simprbi 496 . . . . . . . . . . . . . . . . . 18 (𝑔:𝐵1-1𝐴 → Fun 𝑔)
24 vex 3442 . . . . . . . . . . . . . . . . . . . 20 𝑧 ∈ V
2524fconst 6718 . . . . . . . . . . . . . . . . . . 19 ((𝐴 ∖ ran 𝑔) × {𝑧}):(𝐴 ∖ ran 𝑔)⟶{𝑧}
26 ffun 6663 . . . . . . . . . . . . . . . . . . 19 (((𝐴 ∖ ran 𝑔) × {𝑧}):(𝐴 ∖ ran 𝑔)⟶{𝑧} → Fun ((𝐴 ∖ ran 𝑔) × {𝑧}))
2725, 26ax-mp 5 . . . . . . . . . . . . . . . . . 18 Fun ((𝐴 ∖ ran 𝑔) × {𝑧})
2823, 27jctir 520 . . . . . . . . . . . . . . . . 17 (𝑔:𝐵1-1𝐴 → (Fun 𝑔 ∧ Fun ((𝐴 ∖ ran 𝑔) × {𝑧})))
29 df-rn 5633 . . . . . . . . . . . . . . . . . . . 20 ran 𝑔 = dom 𝑔
3029eqcomi 2743 . . . . . . . . . . . . . . . . . . 19 dom 𝑔 = ran 𝑔
3124snnz 4731 . . . . . . . . . . . . . . . . . . . 20 {𝑧} ≠ ∅
32 dmxp 5876 . . . . . . . . . . . . . . . . . . . 20 ({𝑧} ≠ ∅ → dom ((𝐴 ∖ ran 𝑔) × {𝑧}) = (𝐴 ∖ ran 𝑔))
3331, 32ax-mp 5 . . . . . . . . . . . . . . . . . . 19 dom ((𝐴 ∖ ran 𝑔) × {𝑧}) = (𝐴 ∖ ran 𝑔)
3430, 33ineq12i 4168 . . . . . . . . . . . . . . . . . 18 (dom 𝑔 ∩ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∩ (𝐴 ∖ ran 𝑔))
35 disjdif 4422 . . . . . . . . . . . . . . . . . 18 (ran 𝑔 ∩ (𝐴 ∖ ran 𝑔)) = ∅
3634, 35eqtri 2757 . . . . . . . . . . . . . . . . 17 (dom 𝑔 ∩ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = ∅
37 funun 6536 . . . . . . . . . . . . . . . . 17 (((Fun 𝑔 ∧ Fun ((𝐴 ∖ ran 𝑔) × {𝑧})) ∧ (dom 𝑔 ∩ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = ∅) → Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})))
3828, 36, 37sylancl 586 . . . . . . . . . . . . . . . 16 (𝑔:𝐵1-1𝐴 → Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})))
3938adantl 481 . . . . . . . . . . . . . . 15 ((𝑧𝐵𝑔:𝐵1-1𝐴) → Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})))
40 dmun 5857 . . . . . . . . . . . . . . . . . 18 dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = (dom 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧}))
4129uneq1i 4114 . . . . . . . . . . . . . . . . . 18 (ran 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = (dom 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧}))
4233uneq2i 4115 . . . . . . . . . . . . . . . . . 18 (ran 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔))
4340, 41, 423eqtr2i 2763 . . . . . . . . . . . . . . . . 17 dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔))
44 f1f 6728 . . . . . . . . . . . . . . . . . . 19 (𝑔:𝐵1-1𝐴𝑔:𝐵𝐴)
4544frnd 6668 . . . . . . . . . . . . . . . . . 18 (𝑔:𝐵1-1𝐴 → ran 𝑔𝐴)
46 undif 4432 . . . . . . . . . . . . . . . . . 18 (ran 𝑔𝐴 ↔ (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔)) = 𝐴)
4745, 46sylib 218 . . . . . . . . . . . . . . . . 17 (𝑔:𝐵1-1𝐴 → (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔)) = 𝐴)
4843, 47eqtrid 2781 . . . . . . . . . . . . . . . 16 (𝑔:𝐵1-1𝐴 → dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐴)
4948adantl 481 . . . . . . . . . . . . . . 15 ((𝑧𝐵𝑔:𝐵1-1𝐴) → dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐴)
50 df-fn 6493 . . . . . . . . . . . . . . 15 ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) Fn 𝐴 ↔ (Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∧ dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐴))
5139, 49, 50sylanbrc 583 . . . . . . . . . . . . . 14 ((𝑧𝐵𝑔:𝐵1-1𝐴) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) Fn 𝐴)
52 rnun 6101 . . . . . . . . . . . . . . 15 ran (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧}))
53 dfdm4 5842 . . . . . . . . . . . . . . . . . 18 dom 𝑔 = ran 𝑔
54 f1dm 6732 . . . . . . . . . . . . . . . . . 18 (𝑔:𝐵1-1𝐴 → dom 𝑔 = 𝐵)
5553, 54eqtr3id 2783 . . . . . . . . . . . . . . . . 17 (𝑔:𝐵1-1𝐴 → ran 𝑔 = 𝐵)
5655uneq1d 4117 . . . . . . . . . . . . . . . 16 (𝑔:𝐵1-1𝐴 → (ran 𝑔 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = (𝐵 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})))
57 xpeq1 5636 . . . . . . . . . . . . . . . . . . . . . . 23 ((𝐴 ∖ ran 𝑔) = ∅ → ((𝐴 ∖ ran 𝑔) × {𝑧}) = (∅ × {𝑧}))
58 0xp 5721 . . . . . . . . . . . . . . . . . . . . . . 23 (∅ × {𝑧}) = ∅
5957, 58eqtrdi 2785 . . . . . . . . . . . . . . . . . . . . . 22 ((𝐴 ∖ ran 𝑔) = ∅ → ((𝐴 ∖ ran 𝑔) × {𝑧}) = ∅)
6059rneqd 5885 . . . . . . . . . . . . . . . . . . . . 21 ((𝐴 ∖ ran 𝑔) = ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = ran ∅)
61 rn0 5873 . . . . . . . . . . . . . . . . . . . . 21 ran ∅ = ∅
6260, 61eqtrdi 2785 . . . . . . . . . . . . . . . . . . . 20 ((𝐴 ∖ ran 𝑔) = ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = ∅)
63 0ss 4350 . . . . . . . . . . . . . . . . . . . 20 ∅ ⊆ 𝐵
6462, 63eqsstrdi 3976 . . . . . . . . . . . . . . . . . . 19 ((𝐴 ∖ ran 𝑔) = ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵)
6564a1d 25 . . . . . . . . . . . . . . . . . 18 ((𝐴 ∖ ran 𝑔) = ∅ → (𝑧𝐵 → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵))
66 rnxp 6126 . . . . . . . . . . . . . . . . . . . . 21 ((𝐴 ∖ ran 𝑔) ≠ ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = {𝑧})
6766adantr 480 . . . . . . . . . . . . . . . . . . . 20 (((𝐴 ∖ ran 𝑔) ≠ ∅ ∧ 𝑧𝐵) → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = {𝑧})
68 snssi 4762 . . . . . . . . . . . . . . . . . . . . 21 (𝑧𝐵 → {𝑧} ⊆ 𝐵)
6968adantl 481 . . . . . . . . . . . . . . . . . . . 20 (((𝐴 ∖ ran 𝑔) ≠ ∅ ∧ 𝑧𝐵) → {𝑧} ⊆ 𝐵)
7067, 69eqsstrd 3966 . . . . . . . . . . . . . . . . . . 19 (((𝐴 ∖ ran 𝑔) ≠ ∅ ∧ 𝑧𝐵) → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵)
7170ex 412 . . . . . . . . . . . . . . . . . 18 ((𝐴 ∖ ran 𝑔) ≠ ∅ → (𝑧𝐵 → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵))
7265, 71pm2.61ine 3013 . . . . . . . . . . . . . . . . 17 (𝑧𝐵 → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵)
73 ssequn2 4139 . . . . . . . . . . . . . . . . 17 (ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵 ↔ (𝐵 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
7472, 73sylib 218 . . . . . . . . . . . . . . . 16 (𝑧𝐵 → (𝐵 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
7556, 74sylan9eqr 2791 . . . . . . . . . . . . . . 15 ((𝑧𝐵𝑔:𝐵1-1𝐴) → (ran 𝑔 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
7652, 75eqtrid 2781 . . . . . . . . . . . . . 14 ((𝑧𝐵𝑔:𝐵1-1𝐴) → ran (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
77 df-fo 6496 . . . . . . . . . . . . . 14 ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵 ↔ ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) Fn 𝐴 ∧ ran (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵))
7851, 76, 77sylanbrc 583 . . . . . . . . . . . . 13 ((𝑧𝐵𝑔:𝐵1-1𝐴) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵)
79 foeq1 6740 . . . . . . . . . . . . . 14 (𝑓 = (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) → (𝑓:𝐴onto𝐵 ↔ (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵))
8079spcegv 3549 . . . . . . . . . . . . 13 ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∈ Fin → ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
8121, 78, 80syl2im 40 . . . . . . . . . . . 12 ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → ((𝑧𝐵𝑔:𝐵1-1𝐴) → ∃𝑓 𝑓:𝐴onto𝐵))
8281expcomd 416 . . . . . . . . . . 11 ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑔:𝐵1-1𝐴 → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8382com12 32 . . . . . . . . . 10 (𝑔:𝐵1-1𝐴 → ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8414, 83syland 603 . . . . . . . . 9 (𝑔:𝐵1-1𝐴 → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8584exlimiv 1931 . . . . . . . 8 (∃𝑔 𝑔:𝐵1-1𝐴 → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8610, 85syl 17 . . . . . . 7 (𝐵𝐴 → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8786adantl 481 . . . . . 6 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
888, 9, 87mp2and 699 . . . . 5 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
8988exlimdv 1934 . . . 4 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → (∃𝑧 𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
907, 89syl5 34 . . 3 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → (∅ ≺ 𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
91903impia 1117 . 2 ((𝐴 ∈ Fin ∧ 𝐵𝐴 ∧ ∅ ≺ 𝐵) → ∃𝑓 𝑓:𝐴onto𝐵)
92913com23 1126 1 ((𝐴 ∈ Fin ∧ ∅ ≺ 𝐵𝐵𝐴) → ∃𝑓 𝑓:𝐴onto𝐵)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 206  wa 395  w3a 1086   = wceq 1541  wex 1780  wcel 2113  wne 2930  Vcvv 3438  cdif 3896  cun 3897  cin 3898  wss 3899  c0 4283  {csn 4578   class class class wbr 5096   × cxp 5620  ccnv 5621  dom cdm 5622  ran crn 5623  Fun wfun 6484   Fn wfn 6485  wf 6486  1-1wf1 6487  ontowfo 6488  cdom 8879  csdm 8880  Fincfn 8881
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1911  ax-6 1968  ax-7 2009  ax-8 2115  ax-9 2123  ax-10 2146  ax-11 2162  ax-12 2182  ax-ext 2706  ax-sep 5239  ax-nul 5249  ax-pr 5375  ax-un 7678
This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848  df-3or 1087  df-3an 1088  df-tru 1544  df-fal 1554  df-ex 1781  df-nf 1785  df-sb 2068  df-mo 2537  df-eu 2567  df-clab 2713  df-cleq 2726  df-clel 2809  df-nfc 2883  df-ne 2931  df-ral 3050  df-rex 3059  df-reu 3349  df-rab 3398  df-v 3440  df-sbc 3739  df-dif 3902  df-un 3904  df-in 3906  df-ss 3916  df-pss 3919  df-nul 4284  df-if 4478  df-pw 4554  df-sn 4579  df-pr 4581  df-op 4585  df-uni 4862  df-br 5097  df-opab 5159  df-mpt 5178  df-tr 5204  df-id 5517  df-eprel 5522  df-po 5530  df-so 5531  df-fr 5575  df-we 5577  df-xp 5628  df-rel 5629  df-cnv 5630  df-co 5631  df-dm 5632  df-rn 5633  df-res 5634  df-ima 5635  df-ord 6318  df-on 6319  df-lim 6320  df-suc 6321  df-iota 6446  df-fun 6492  df-fn 6493  df-f 6494  df-f1 6495  df-fo 6496  df-f1o 6497  df-fv 6498  df-om 7807  df-1o 8395  df-en 8882  df-dom 8883  df-sdom 8884  df-fin 8885
This theorem is referenced by:  fodomfib  9227
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