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Theorem fodomfir 9283
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 9112). (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 8946 . . . . . . 7 Rel ≺
21brrelex2i 5718 . . . . . 6 (∅ ≺ 𝐵𝐵 ∈ V)
3 0sdomg 9090 . . . . . . 7 (𝐵 ∈ V → (∅ ≺ 𝐵𝐵 ≠ ∅))
4 n0 4307 . . . . . . 7 (𝐵 ≠ ∅ ↔ ∃𝑧 𝑧𝐵)
53, 4bitrdi 290 . . . . . 6 (𝐵 ∈ V → (∅ ≺ 𝐵 ↔ ∃𝑧 𝑧𝐵))
62, 5syl 18 . . . . 5 (∅ ≺ 𝐵 → (∅ ≺ 𝐵 ↔ ∃𝑧 𝑧𝐵))
76ibi 270 . . . 4 (∅ ≺ 𝐵 → ∃𝑧 𝑧𝐵)
8 domfi 9169 . . . . . 6 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → 𝐵 ∈ Fin)
9 simpl 487 . . . . . 6 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → 𝐴 ∈ Fin)
10 brdomi 8952 . . . . . . . 8 (𝐵𝐴 → ∃𝑔 𝑔:𝐵1-1𝐴)
11 f1fn 6775 . . . . . . . . . . . 12 (𝑔:𝐵1-1𝐴𝑔 Fn 𝐵)
12 fnfi 9158 . . . . . . . . . . . 12 ((𝑔 Fn 𝐵𝐵 ∈ Fin) → 𝑔 ∈ Fin)
1311, 12sylan 591 . . . . . . . . . . 11 ((𝑔:𝐵1-1𝐴𝐵 ∈ Fin) → 𝑔 ∈ Fin)
1413ex 417 . . . . . . . . . 10 (𝑔:𝐵1-1𝐴 → (𝐵 ∈ Fin → 𝑔 ∈ Fin))
15 cnvfi 9156 . . . . . . . . . . . . . 14 (𝑔 ∈ Fin → 𝑔 ∈ Fin)
16 diffi 9155 . . . . . . . . . . . . . . 15 (𝐴 ∈ Fin → (𝐴 ∖ ran 𝑔) ∈ Fin)
17 snfi 9036 . . . . . . . . . . . . . . 15 {𝑧} ∈ Fin
18 xpfi 9275 . . . . . . . . . . . . . . 15 (((𝐴 ∖ ran 𝑔) ∈ Fin ∧ {𝑧} ∈ Fin) → ((𝐴 ∖ ran 𝑔) × {𝑧}) ∈ Fin)
1916, 17, 18sylancl 597 . . . . . . . . . . . . . 14 (𝐴 ∈ Fin → ((𝐴 ∖ ran 𝑔) × {𝑧}) ∈ Fin)
20 unfi 9151 . . . . . . . . . . . . . 14 ((𝑔 ∈ Fin ∧ ((𝐴 ∖ ran 𝑔) × {𝑧}) ∈ Fin) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∈ Fin)
2115, 19, 20syl2an 607 . . . . . . . . . . . . 13 ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∈ Fin)
22 df-f1 6541 . . . . . . . . . . . . . . . . . . 19 (𝑔:𝐵1-1𝐴 ↔ (𝑔:𝐵𝐴 ∧ Fun 𝑔))
2322simprbi 502 . . . . . . . . . . . . . . . . . 18 (𝑔:𝐵1-1𝐴 → Fun 𝑔)
24 vex 3459 . . . . . . . . . . . . . . . . . . . 20 𝑧 ∈ V
2524fconst 6764 . . . . . . . . . . . . . . . . . . 19 ((𝐴 ∖ ran 𝑔) × {𝑧}):(𝐴 ∖ ran 𝑔)⟶{𝑧}
26 ffun 6708 . . . . . . . . . . . . . . . . . . 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 529 . . . . . . . . . . . . . . . . 17 (𝑔:𝐵1-1𝐴 → (Fun 𝑔 ∧ Fun ((𝐴 ∖ ran 𝑔) × {𝑧})))
29 df-rn 5672 . . . . . . . . . . . . . . . . . . . 20 ran 𝑔 = dom 𝑔
3029eqcomi 2772 . . . . . . . . . . . . . . . . . . 19 dom 𝑔 = ran 𝑔
3124snnz 4742 . . . . . . . . . . . . . . . . . . . 20 {𝑧} ≠ ∅
32 dmxp 5919 . . . . . . . . . . . . . . . . . . . 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 4171 . . . . . . . . . . . . . . . . . 18 (dom 𝑔 ∩ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∩ (𝐴 ∖ ran 𝑔))
35 disjdif 4433 . . . . . . . . . . . . . . . . . 18 (ran 𝑔 ∩ (𝐴 ∖ ran 𝑔)) = ∅
3634, 35eqtri 2786 . . . . . . . . . . . . . . . . 17 (dom 𝑔 ∩ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = ∅
37 funun 6582 . . . . . . . . . . . . . . . . 17 (((Fun 𝑔 ∧ Fun ((𝐴 ∖ ran 𝑔) × {𝑧})) ∧ (dom 𝑔 ∩ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = ∅) → Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})))
3828, 36, 37sylancl 597 . . . . . . . . . . . . . . . 16 (𝑔:𝐵1-1𝐴 → Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})))
3938adantl 486 . . . . . . . . . . . . . . 15 ((𝑧𝐵𝑔:𝐵1-1𝐴) → Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})))
40 dmun 5900 . . . . . . . . . . . . . . . . . 18 dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = (dom 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧}))
4129uneq1i 4118 . . . . . . . . . . . . . . . . . 18 (ran 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = (dom 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧}))
4233uneq2i 4119 . . . . . . . . . . . . . . . . . 18 (ran 𝑔 ∪ dom ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔))
4340, 41, 423eqtr2i 2792 . . . . . . . . . . . . . . . . 17 dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔))
44 f1f 6774 . . . . . . . . . . . . . . . . . . 19 (𝑔:𝐵1-1𝐴𝑔:𝐵𝐴)
4544frnd 6714 . . . . . . . . . . . . . . . . . 18 (𝑔:𝐵1-1𝐴 → ran 𝑔𝐴)
46 undif 4443 . . . . . . . . . . . . . . . . . 18 (ran 𝑔𝐴 ↔ (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔)) = 𝐴)
4745, 46sylib 221 . . . . . . . . . . . . . . . . 17 (𝑔:𝐵1-1𝐴 → (ran 𝑔 ∪ (𝐴 ∖ ran 𝑔)) = 𝐴)
4843, 47eqtrid 2810 . . . . . . . . . . . . . . . 16 (𝑔:𝐵1-1𝐴 → dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐴)
4948adantl 486 . . . . . . . . . . . . . . 15 ((𝑧𝐵𝑔:𝐵1-1𝐴) → dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐴)
50 df-fn 6539 . . . . . . . . . . . . . . 15 ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) Fn 𝐴 ↔ (Fun (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∧ dom (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐴))
5139, 49, 50sylanbrc 594 . . . . . . . . . . . . . 14 ((𝑧𝐵𝑔:𝐵1-1𝐴) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) Fn 𝐴)
52 rnun 6142 . . . . . . . . . . . . . . 15 ran (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = (ran 𝑔 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧}))
53 dfdm4 5885 . . . . . . . . . . . . . . . . . 18 dom 𝑔 = ran 𝑔
54 f1dm 6780 . . . . . . . . . . . . . . . . . 18 (𝑔:𝐵1-1𝐴 → dom 𝑔 = 𝐵)
5553, 54eqtr3id 2812 . . . . . . . . . . . . . . . . 17 (𝑔:𝐵1-1𝐴 → ran 𝑔 = 𝐵)
5655uneq1d 4121 . . . . . . . . . . . . . . . 16 (𝑔:𝐵1-1𝐴 → (ran 𝑔 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = (𝐵 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})))
57 xpeq1 5675 . . . . . . . . . . . . . . . . . . . . . . 23 ((𝐴 ∖ ran 𝑔) = ∅ → ((𝐴 ∖ ran 𝑔) × {𝑧}) = (∅ × {𝑧}))
58 0xp 5760 . . . . . . . . . . . . . . . . . . . . . . 23 (∅ × {𝑧}) = ∅
5957, 58eqtrdi 2814 . . . . . . . . . . . . . . . . . . . . . 22 ((𝐴 ∖ ran 𝑔) = ∅ → ((𝐴 ∖ ran 𝑔) × {𝑧}) = ∅)
6059rneqd 5928 . . . . . . . . . . . . . . . . . . . . 21 ((𝐴 ∖ ran 𝑔) = ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = ran ∅)
61 rn0 5916 . . . . . . . . . . . . . . . . . . . . 21 ran ∅ = ∅
6260, 61eqtrdi 2814 . . . . . . . . . . . . . . . . . . . 20 ((𝐴 ∖ ran 𝑔) = ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = ∅)
63 0ss 4357 . . . . . . . . . . . . . . . . . . . 20 ∅ ⊆ 𝐵
6462, 63eqsstrdi 3981 . . . . . . . . . . . . . . . . . . 19 ((𝐴 ∖ ran 𝑔) = ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵)
6564a1d 26 . . . . . . . . . . . . . . . . . 18 ((𝐴 ∖ ran 𝑔) = ∅ → (𝑧𝐵 → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵))
66 rnxp 6168 . . . . . . . . . . . . . . . . . . . . 21 ((𝐴 ∖ ran 𝑔) ≠ ∅ → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = {𝑧})
6766adantr 485 . . . . . . . . . . . . . . . . . . . 20 (((𝐴 ∖ ran 𝑔) ≠ ∅ ∧ 𝑧𝐵) → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) = {𝑧})
68 snssi 4751 . . . . . . . . . . . . . . . . . . . . 21 (𝑧𝐵 → {𝑧} ⊆ 𝐵)
6968adantl 486 . . . . . . . . . . . . . . . . . . . 20 (((𝐴 ∖ ran 𝑔) ≠ ∅ ∧ 𝑧𝐵) → {𝑧} ⊆ 𝐵)
7067, 69eqsstrd 3971 . . . . . . . . . . . . . . . . . . 19 (((𝐴 ∖ ran 𝑔) ≠ ∅ ∧ 𝑧𝐵) → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵)
7170ex 417 . . . . . . . . . . . . . . . . . 18 ((𝐴 ∖ ran 𝑔) ≠ ∅ → (𝑧𝐵 → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵))
7265, 71pm2.61ine 3041 . . . . . . . . . . . . . . . . 17 (𝑧𝐵 → ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵)
73 ssequn2 4142 . . . . . . . . . . . . . . . . 17 (ran ((𝐴 ∖ ran 𝑔) × {𝑧}) ⊆ 𝐵 ↔ (𝐵 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
7472, 73sylib 221 . . . . . . . . . . . . . . . 16 (𝑧𝐵 → (𝐵 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
7556, 74sylan9eqr 2820 . . . . . . . . . . . . . . 15 ((𝑧𝐵𝑔:𝐵1-1𝐴) → (ran 𝑔 ∪ ran ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
7652, 75eqtrid 2810 . . . . . . . . . . . . . 14 ((𝑧𝐵𝑔:𝐵1-1𝐴) → ran (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵)
77 df-fo 6542 . . . . . . . . . . . . . 14 ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵 ↔ ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) Fn 𝐴 ∧ ran (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) = 𝐵))
7851, 76, 77sylanbrc 594 . . . . . . . . . . . . 13 ((𝑧𝐵𝑔:𝐵1-1𝐴) → (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵)
79 foeq1 6788 . . . . . . . . . . . . . 14 (𝑓 = (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) → (𝑓:𝐴onto𝐵 ↔ (𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵))
8079spcegv 3556 . . . . . . . . . . . . 13 ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})) ∈ Fin → ((𝑔 ∪ ((𝐴 ∖ ran 𝑔) × {𝑧})):𝐴onto𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
8121, 78, 80syl2im 41 . . . . . . . . . . . 12 ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → ((𝑧𝐵𝑔:𝐵1-1𝐴) → ∃𝑓 𝑓:𝐴onto𝐵))
8281expcomd 421 . . . . . . . . . . 11 ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑔:𝐵1-1𝐴 → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8382com12 33 . . . . . . . . . 10 (𝑔:𝐵1-1𝐴 → ((𝑔 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8414, 83syland 614 . . . . . . . . 9 (𝑔:𝐵1-1𝐴 → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8584exlimiv 1960 . . . . . . . 8 (∃𝑔 𝑔:𝐵1-1𝐴 → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8610, 85syl 18 . . . . . . 7 (𝐵𝐴 → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
8786adantl 486 . . . . . 6 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → ((𝐵 ∈ Fin ∧ 𝐴 ∈ Fin) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵)))
888, 9, 87mp2and 711 . . . . 5 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → (𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
8988exlimdv 1963 . . . 4 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → (∃𝑧 𝑧𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
907, 89syl5 35 . . 3 ((𝐴 ∈ Fin ∧ 𝐵𝐴) → (∅ ≺ 𝐵 → ∃𝑓 𝑓:𝐴onto𝐵))
91903impia 1135 . 2 ((𝐴 ∈ Fin ∧ 𝐵𝐴 ∧ ∅ ≺ 𝐵) → ∃𝑓 𝑓:𝐴onto𝐵)
92913com23 1144 1 ((𝐴 ∈ Fin ∧ ∅ ≺ 𝐵𝐵𝐴) → ∃𝑓 𝑓:𝐴onto𝐵)
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 209  wa 400  w3a 1103   = wceq 1570  wex 1809  wcel 2143  wne 2958  Vcvv 3455  cdif 3902  cun 3903  cin 3904  wss 3905  c0 4286  {csn 4589   class class class wbr 5109   × cxp 5659  ccnv 5660  dom cdm 5661  ran crn 5662  Fun wfun 6530   Fn wfn 6531  wf 6532  1-1wf1 6533  ontowfo 6534  cdom 8937  csdm 8938  Fincfn 8939
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1825  ax-4 1839  ax-5 1940  ax-6 1997  ax-7 2038  ax-8 2145  ax-9 2153  ax-10 2176  ax-11 2192  ax-12 2213  ax-ext 2735  ax-sep 5257  ax-nul 5269  ax-pr 5404  ax-un 7732
This theorem depends on definitions:  df-bi 210  df-an 401  df-or 861  df-3or 1104  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1810  df-nf 1814  df-sb 2097  df-mo 2567  df-eu 2597  df-clab 2742  df-cleq 2755  df-clel 2838  df-nfc 2912  df-ne 2959  df-ral 3080  df-rex 3090  df-reu 3370  df-rab 3417  df-v 3457  df-sbc 3745  df-dif 3908  df-un 3910  df-in 3912  df-ss 3922  df-pss 3925  df-nul 4287  df-if 4488  df-pw 4564  df-sn 4590  df-pr 4592  df-op 4596  df-uni 4873  df-br 5110  df-opab 5174  df-mpt 5193  df-tr 5219  df-id 5556  df-eprel 5561  df-po 5569  df-so 5570  df-fr 5614  df-we 5616  df-xp 5667  df-rel 5668  df-cnv 5669  df-co 5670  df-dm 5671  df-rn 5672  df-res 5673  df-ima 5674  df-ord 6363  df-on 6364  df-lim 6365  df-suc 6366  df-iota 6492  df-fun 6538  df-fn 6539  df-f 6540  df-f1 6541  df-fo 6542  df-f1o 6543  df-fv 6544  df-om 7859  df-1o 8449  df-en 8940  df-dom 8941  df-sdom 8942  df-fin 8943
This theorem is referenced by:  fodomfib  9284
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