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Mirrors > Home > MPE Home > Th. List > ac5 | Structured version Visualization version GIF version |
Description: An Axiom of Choice equivalent: there exists a function 𝑓 (called a choice function) with domain 𝐴 that maps each nonempty member of the domain to an element of that member. Axiom AC of [BellMachover] p. 488. Note that the assertion that 𝑓 be a function is not necessary; see ac4 9897. (Contributed by NM, 29-Aug-1999.) |
Ref | Expression |
---|---|
ac5.1 | ⊢ 𝐴 ∈ V |
Ref | Expression |
---|---|
ac5 | ⊢ ∃𝑓(𝑓 Fn 𝐴 ∧ ∀𝑥 ∈ 𝐴 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ac5.1 | . 2 ⊢ 𝐴 ∈ V | |
2 | fneq2 6445 | . . . 4 ⊢ (𝑦 = 𝐴 → (𝑓 Fn 𝑦 ↔ 𝑓 Fn 𝐴)) | |
3 | raleq 3405 | . . . 4 ⊢ (𝑦 = 𝐴 → (∀𝑥 ∈ 𝑦 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥) ↔ ∀𝑥 ∈ 𝐴 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥))) | |
4 | 2, 3 | anbi12d 632 | . . 3 ⊢ (𝑦 = 𝐴 → ((𝑓 Fn 𝑦 ∧ ∀𝑥 ∈ 𝑦 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥)) ↔ (𝑓 Fn 𝐴 ∧ ∀𝑥 ∈ 𝐴 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥)))) |
5 | 4 | exbidv 1922 | . 2 ⊢ (𝑦 = 𝐴 → (∃𝑓(𝑓 Fn 𝑦 ∧ ∀𝑥 ∈ 𝑦 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥)) ↔ ∃𝑓(𝑓 Fn 𝐴 ∧ ∀𝑥 ∈ 𝐴 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥)))) |
6 | dfac4 9548 | . . 3 ⊢ (CHOICE ↔ ∀𝑦∃𝑓(𝑓 Fn 𝑦 ∧ ∀𝑥 ∈ 𝑦 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥))) | |
7 | 6 | axaci 9890 | . 2 ⊢ ∃𝑓(𝑓 Fn 𝑦 ∧ ∀𝑥 ∈ 𝑦 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥)) |
8 | 1, 5, 7 | vtocl 3559 | 1 ⊢ ∃𝑓(𝑓 Fn 𝐴 ∧ ∀𝑥 ∈ 𝐴 (𝑥 ≠ ∅ → (𝑓‘𝑥) ∈ 𝑥)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 398 = wceq 1537 ∃wex 1780 ∈ wcel 2114 ≠ wne 3016 ∀wral 3138 Vcvv 3494 ∅c0 4291 Fn wfn 6350 ‘cfv 6355 |
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 1970 ax-7 2015 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2161 ax-12 2177 ax-ext 2793 ax-rep 5190 ax-sep 5203 ax-nul 5210 ax-pow 5266 ax-pr 5330 ax-un 7461 ax-ac2 9885 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-3an 1085 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 df-mo 2622 df-eu 2654 df-clab 2800 df-cleq 2814 df-clel 2893 df-nfc 2963 df-ne 3017 df-ral 3143 df-rex 3144 df-reu 3145 df-rab 3147 df-v 3496 df-sbc 3773 df-csb 3884 df-dif 3939 df-un 3941 df-in 3943 df-ss 3952 df-nul 4292 df-if 4468 df-pw 4541 df-sn 4568 df-pr 4570 df-op 4574 df-uni 4839 df-iun 4921 df-br 5067 df-opab 5129 df-mpt 5147 df-id 5460 df-xp 5561 df-rel 5562 df-cnv 5563 df-co 5564 df-dm 5565 df-rn 5566 df-res 5567 df-ima 5568 df-iota 6314 df-fun 6357 df-fn 6358 df-f 6359 df-f1 6360 df-fo 6361 df-f1o 6362 df-fv 6363 df-ac 9542 |
This theorem is referenced by: (None) |
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