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Mirrors > Home > ILE Home > Th. List > peano1 | GIF version |
Description: Zero is a natural number. One of Peano's five postulates for arithmetic. Proposition 7.30(1) of [TakeutiZaring] p. 42. (Contributed by NM, 15-May-1994.) |
Ref | Expression |
---|---|
peano1 | ⊢ ∅ ∈ ω |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0ex 4050 | . . . 4 ⊢ ∅ ∈ V | |
2 | 1 | elint 3772 | . . 3 ⊢ (∅ ∈ ∩ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} ↔ ∀𝑧(𝑧 ∈ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} → ∅ ∈ 𝑧)) |
3 | df-clab 2124 | . . . 4 ⊢ (𝑧 ∈ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} ↔ [𝑧 / 𝑦](∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)) | |
4 | simpl 108 | . . . . . 6 ⊢ ((∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦) → ∅ ∈ 𝑦) | |
5 | 4 | sbimi 1737 | . . . . 5 ⊢ ([𝑧 / 𝑦](∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦) → [𝑧 / 𝑦]∅ ∈ 𝑦) |
6 | clelsb4 2243 | . . . . 5 ⊢ ([𝑧 / 𝑦]∅ ∈ 𝑦 ↔ ∅ ∈ 𝑧) | |
7 | 5, 6 | sylib 121 | . . . 4 ⊢ ([𝑧 / 𝑦](∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦) → ∅ ∈ 𝑧) |
8 | 3, 7 | sylbi 120 | . . 3 ⊢ (𝑧 ∈ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} → ∅ ∈ 𝑧) |
9 | 2, 8 | mpgbir 1429 | . 2 ⊢ ∅ ∈ ∩ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} |
10 | dfom3 4501 | . 2 ⊢ ω = ∩ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} | |
11 | 9, 10 | eleqtrri 2213 | 1 ⊢ ∅ ∈ ω |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 103 ∈ wcel 1480 [wsb 1735 {cab 2123 ∀wral 2414 ∅c0 3358 ∩ cint 3766 suc csuc 4282 ωcom 4499 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 603 ax-in2 604 ax-io 698 ax-5 1423 ax-7 1424 ax-gen 1425 ax-ie1 1469 ax-ie2 1470 ax-8 1482 ax-10 1483 ax-11 1484 ax-i12 1485 ax-bndl 1486 ax-4 1487 ax-17 1506 ax-i9 1510 ax-ial 1514 ax-i5r 1515 ax-ext 2119 ax-nul 4049 |
This theorem depends on definitions: df-bi 116 df-tru 1334 df-nf 1437 df-sb 1736 df-clab 2124 df-cleq 2130 df-clel 2133 df-nfc 2268 df-v 2683 df-dif 3068 df-nul 3359 df-int 3767 df-iom 4500 |
This theorem is referenced by: peano5 4507 limom 4522 nnregexmid 4529 omsinds 4530 nnpredcl 4531 frec0g 6287 frecabcl 6289 frecrdg 6298 oa1suc 6356 nna0r 6367 nnm0r 6368 nnmcl 6370 nnmsucr 6377 1onn 6409 nnm1 6413 nnaordex 6416 nnawordex 6417 php5 6745 php5dom 6750 0fin 6771 findcard2 6776 findcard2s 6777 infm 6791 inffiexmid 6793 0ct 6985 ctmlemr 6986 ctssdclemn0 6988 ctssdc 6991 omct 6995 fodjum 7011 fodju0 7012 ctssexmid 7017 1lt2pi 7141 nq0m0r 7257 nq0a0 7258 prarloclem5 7301 frec2uzrand 10171 frecuzrdg0 10179 frecuzrdg0t 10188 frecfzennn 10192 0tonninf 10205 1tonninf 10206 hashinfom 10517 hashunlem 10543 hash1 10550 ennnfonelemj0 11903 ennnfonelem1 11909 ennnfonelemhf1o 11915 ennnfonelemhom 11917 bj-nn0suc 13151 bj-nn0sucALT 13165 pwle2 13182 pwf1oexmid 13183 subctctexmid 13185 peano3nninf 13190 nninfall 13193 nninfsellemdc 13195 nninfsellemeq 13199 nninffeq 13205 isomninnlem 13214 |
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