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Mirrors > Home > MPE Home > Th. List > 0npi | Structured version Visualization version GIF version |
Description: The empty set is not a positive integer. (Contributed by NM, 26-Aug-1995.) (New usage is discouraged.) |
Ref | Expression |
---|---|
0npi | ⊢ ¬ ∅ ∈ N |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqid 2825 | . 2 ⊢ ∅ = ∅ | |
2 | elni 10020 | . . . 4 ⊢ (∅ ∈ N ↔ (∅ ∈ ω ∧ ∅ ≠ ∅)) | |
3 | 2 | simprbi 492 | . . 3 ⊢ (∅ ∈ N → ∅ ≠ ∅) |
4 | 3 | necon2bi 3029 | . 2 ⊢ (∅ = ∅ → ¬ ∅ ∈ N) |
5 | 1, 4 | ax-mp 5 | 1 ⊢ ¬ ∅ ∈ N |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 = wceq 1656 ∈ wcel 2164 ≠ wne 2999 ∅c0 4146 ωcom 7331 Ncnpi 9988 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1894 ax-4 1908 ax-5 2009 ax-6 2075 ax-7 2112 ax-9 2173 ax-10 2192 ax-11 2207 ax-12 2220 ax-ext 2803 |
This theorem depends on definitions: df-bi 199 df-an 387 df-or 879 df-tru 1660 df-ex 1879 df-nf 1883 df-sb 2068 df-clab 2812 df-cleq 2818 df-clel 2821 df-nfc 2958 df-ne 3000 df-v 3416 df-dif 3801 df-sn 4400 df-ni 10016 |
This theorem is referenced by: addasspi 10039 mulasspi 10041 distrpi 10042 addcanpi 10043 mulcanpi 10044 addnidpi 10045 ltapi 10047 ltmpi 10048 ordpipq 10086 |
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