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Theorem peano2nn 8732
Description: Peano postulate: a successor of a positive integer is a positive integer. (Contributed by NM, 11-Jan-1997.) (Revised by Mario Carneiro, 17-Nov-2014.)
Assertion
Ref Expression
peano2nn (𝐴 ∈ ℕ → (𝐴 + 1) ∈ ℕ)

Proof of Theorem peano2nn
Dummy variables 𝑥 𝑦 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 dfnn2 8722 . . . . . 6 ℕ = {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)}
21eleq2i 2206 . . . . 5 (𝐴 ∈ ℕ ↔ 𝐴 {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)})
3 elintg 3779 . . . . 5 (𝐴 ∈ ℕ → (𝐴 {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} ↔ ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)}𝐴𝑧))
42, 3syl5bb 191 . . . 4 (𝐴 ∈ ℕ → (𝐴 ∈ ℕ ↔ ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)}𝐴𝑧))
54ibi 175 . . 3 (𝐴 ∈ ℕ → ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)}𝐴𝑧)
6 vex 2689 . . . . . . . 8 𝑧 ∈ V
7 eleq2 2203 . . . . . . . . 9 (𝑥 = 𝑧 → (1 ∈ 𝑥 ↔ 1 ∈ 𝑧))
8 eleq2 2203 . . . . . . . . . 10 (𝑥 = 𝑧 → ((𝑦 + 1) ∈ 𝑥 ↔ (𝑦 + 1) ∈ 𝑧))
98raleqbi1dv 2634 . . . . . . . . 9 (𝑥 = 𝑧 → (∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥 ↔ ∀𝑦𝑧 (𝑦 + 1) ∈ 𝑧))
107, 9anbi12d 464 . . . . . . . 8 (𝑥 = 𝑧 → ((1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥) ↔ (1 ∈ 𝑧 ∧ ∀𝑦𝑧 (𝑦 + 1) ∈ 𝑧)))
116, 10elab 2828 . . . . . . 7 (𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} ↔ (1 ∈ 𝑧 ∧ ∀𝑦𝑧 (𝑦 + 1) ∈ 𝑧))
1211simprbi 273 . . . . . 6 (𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} → ∀𝑦𝑧 (𝑦 + 1) ∈ 𝑧)
13 oveq1 5781 . . . . . . . 8 (𝑦 = 𝐴 → (𝑦 + 1) = (𝐴 + 1))
1413eleq1d 2208 . . . . . . 7 (𝑦 = 𝐴 → ((𝑦 + 1) ∈ 𝑧 ↔ (𝐴 + 1) ∈ 𝑧))
1514rspcva 2787 . . . . . 6 ((𝐴𝑧 ∧ ∀𝑦𝑧 (𝑦 + 1) ∈ 𝑧) → (𝐴 + 1) ∈ 𝑧)
1612, 15sylan2 284 . . . . 5 ((𝐴𝑧𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)}) → (𝐴 + 1) ∈ 𝑧)
1716expcom 115 . . . 4 (𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} → (𝐴𝑧 → (𝐴 + 1) ∈ 𝑧))
1817ralimia 2493 . . 3 (∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)}𝐴𝑧 → ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} (𝐴 + 1) ∈ 𝑧)
195, 18syl 14 . 2 (𝐴 ∈ ℕ → ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} (𝐴 + 1) ∈ 𝑧)
20 nnre 8727 . . . 4 (𝐴 ∈ ℕ → 𝐴 ∈ ℝ)
21 1red 7781 . . . 4 (𝐴 ∈ ℕ → 1 ∈ ℝ)
2220, 21readdcld 7795 . . 3 (𝐴 ∈ ℕ → (𝐴 + 1) ∈ ℝ)
231eleq2i 2206 . . . 4 ((𝐴 + 1) ∈ ℕ ↔ (𝐴 + 1) ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)})
24 elintg 3779 . . . 4 ((𝐴 + 1) ∈ ℝ → ((𝐴 + 1) ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} ↔ ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} (𝐴 + 1) ∈ 𝑧))
2523, 24syl5bb 191 . . 3 ((𝐴 + 1) ∈ ℝ → ((𝐴 + 1) ∈ ℕ ↔ ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} (𝐴 + 1) ∈ 𝑧))
2622, 25syl 14 . 2 (𝐴 ∈ ℕ → ((𝐴 + 1) ∈ ℕ ↔ ∀𝑧 ∈ {𝑥 ∣ (1 ∈ 𝑥 ∧ ∀𝑦𝑥 (𝑦 + 1) ∈ 𝑥)} (𝐴 + 1) ∈ 𝑧))
2719, 26mpbird 166 1 (𝐴 ∈ ℕ → (𝐴 + 1) ∈ ℕ)
Colors of variables: wff set class
Syntax hints:  wi 4  wa 103  wb 104   = wceq 1331  wcel 1480  {cab 2125  wral 2416   cint 3771  (class class class)co 5774  cr 7619  1c1 7621   + caddc 7623  cn 8720
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-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 2121  ax-sep 4046  ax-cnex 7711  ax-resscn 7712  ax-1re 7714  ax-addrcl 7717
This theorem depends on definitions:  df-bi 116  df-3an 964  df-tru 1334  df-nf 1437  df-sb 1736  df-clab 2126  df-cleq 2132  df-clel 2135  df-nfc 2270  df-ral 2421  df-rex 2422  df-v 2688  df-un 3075  df-in 3077  df-ss 3084  df-sn 3533  df-pr 3534  df-op 3536  df-uni 3737  df-int 3772  df-br 3930  df-iota 5088  df-fv 5131  df-ov 5777  df-inn 8721
This theorem is referenced by:  peano2nnd  8735  nnind  8736  nnaddcl  8740  2nn  8881  3nn  8882  4nn  8883  5nn  8884  6nn  8885  7nn  8886  8nn  8887  9nn  8888  nneoor  9153  10nn  9197  nnsplit  9914  fzonn0p1p1  9990  expp1  10300  facp1  10476  resqrexlemfp1  10781  resqrexlemcalc3  10788  trireciplem  11269  trirecip  11270  cvgratnnlemnexp  11293  cvgratz  11301  nno  11603  nnoddm1d2  11607  rplpwr  11715  prmind2  11801  sqrt2irr  11840
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