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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 4063 | . . . 4 ⊢ ∅ ∈ V | |
2 | 1 | elint 3785 | . . 3 ⊢ (∅ ∈ ∩ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} ↔ ∀𝑧(𝑧 ∈ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} → ∅ ∈ 𝑧)) |
3 | df-clab 2127 | . . . 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 1738 | . . . . 5 ⊢ ([𝑧 / 𝑦](∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦) → [𝑧 / 𝑦]∅ ∈ 𝑦) |
6 | clelsb4 2246 | . . . . 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 1430 | . 2 ⊢ ∅ ∈ ∩ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} |
10 | dfom3 4514 | . 2 ⊢ ω = ∩ {𝑦 ∣ (∅ ∈ 𝑦 ∧ ∀𝑥 ∈ 𝑦 suc 𝑥 ∈ 𝑦)} | |
11 | 9, 10 | eleqtrri 2216 | 1 ⊢ ∅ ∈ ω |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 103 ∈ wcel 1481 [wsb 1736 {cab 2126 ∀wral 2417 ∅c0 3368 ∩ cint 3779 suc csuc 4295 ωcom 4512 |
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 604 ax-in2 605 ax-io 699 ax-5 1424 ax-7 1425 ax-gen 1426 ax-ie1 1470 ax-ie2 1471 ax-8 1483 ax-10 1484 ax-11 1485 ax-i12 1486 ax-bndl 1487 ax-4 1488 ax-17 1507 ax-i9 1511 ax-ial 1515 ax-i5r 1516 ax-ext 2122 ax-nul 4062 |
This theorem depends on definitions: df-bi 116 df-tru 1335 df-nf 1438 df-sb 1737 df-clab 2127 df-cleq 2133 df-clel 2136 df-nfc 2271 df-v 2691 df-dif 3078 df-nul 3369 df-int 3780 df-iom 4513 |
This theorem is referenced by: peano5 4520 limom 4535 nnregexmid 4542 omsinds 4543 nnpredcl 4544 frec0g 6302 frecabcl 6304 frecrdg 6313 oa1suc 6371 nna0r 6382 nnm0r 6383 nnmcl 6385 nnmsucr 6392 1onn 6424 nnm1 6428 nnaordex 6431 nnawordex 6432 php5 6760 php5dom 6765 0fin 6786 findcard2 6791 findcard2s 6792 infm 6806 inffiexmid 6808 0ct 7000 ctmlemr 7001 ctssdclemn0 7003 ctssdc 7006 omct 7010 fodjum 7026 fodju0 7027 ctssexmid 7032 1lt2pi 7172 nq0m0r 7288 nq0a0 7289 prarloclem5 7332 frec2uzrand 10209 frecuzrdg0 10217 frecuzrdg0t 10226 frecfzennn 10230 0tonninf 10243 1tonninf 10244 hashinfom 10556 hashunlem 10582 hash1 10589 ennnfonelemj0 11950 ennnfonelem1 11956 ennnfonelemhf1o 11962 ennnfonelemhom 11964 bj-nn0suc 13333 bj-nn0sucALT 13347 012of 13363 2o01f 13364 pwle2 13366 pwf1oexmid 13367 subctctexmid 13369 peano3nninf 13376 nninfall 13379 nninfsellemdc 13381 nninfsellemeq 13385 nninffeq 13391 isomninnlem 13400 iswomninnlem 13417 ismkvnnlem 13419 |
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