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Theorem elni 10914
Description: Membership in the class of positive integers. (Contributed by NM, 15-Aug-1995.) (New usage is discouraged.)
Assertion
Ref Expression
elni (𝐴N ↔ (𝐴 ∈ ω ∧ 𝐴 ≠ ∅))

Proof of Theorem elni
StepHypRef Expression
1 df-ni 10910 . . 3 N = (ω ∖ {∅})
21eleq2i 2831 . 2 (𝐴N𝐴 ∈ (ω ∖ {∅}))
3 eldifsn 4791 . 2 (𝐴 ∈ (ω ∖ {∅}) ↔ (𝐴 ∈ ω ∧ 𝐴 ≠ ∅))
42, 3bitri 275 1 (𝐴N ↔ (𝐴 ∈ ω ∧ 𝐴 ≠ ∅))
Colors of variables: wff setvar class
Syntax hints:  wb 206  wa 395  wcel 2106  wne 2938  cdif 3960  c0 4339  {csn 4631  ωcom 7887  Ncnpi 10882
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1792  ax-4 1806  ax-5 1908  ax-6 1965  ax-7 2005  ax-8 2108  ax-9 2116  ax-ext 2706
This theorem depends on definitions:  df-bi 207  df-an 396  df-tru 1540  df-ex 1777  df-sb 2063  df-clab 2713  df-cleq 2727  df-clel 2814  df-ne 2939  df-v 3480  df-dif 3966  df-sn 4632  df-ni 10910
This theorem is referenced by:  elni2  10915  0npi  10920  1pi  10921  addclpi  10930  mulclpi  10931  nlt1pi  10944  indpi  10945
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