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Mirrors > Home > MPE Home > Th. List > neq0 | Structured version Visualization version GIF version |
Description: A class is not empty if and only if it has at least one element. Proposition 5.17(1) of [TakeutiZaring] p. 20. (Contributed by NM, 21-Jun-1993.) Avoid ax-11 2155, ax-12 2172. (Revised by Gino Giotto, 28-Jun-2024.) |
Ref | Expression |
---|---|
neq0 | ⊢ (¬ 𝐴 = ∅ ↔ ∃𝑥 𝑥 ∈ 𝐴) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-ex 1783 | . . 3 ⊢ (∃𝑥 𝑥 ∈ 𝐴 ↔ ¬ ∀𝑥 ¬ 𝑥 ∈ 𝐴) | |
2 | eq0 4344 | . . 3 ⊢ (𝐴 = ∅ ↔ ∀𝑥 ¬ 𝑥 ∈ 𝐴) | |
3 | 1, 2 | xchbinxr 335 | . 2 ⊢ (∃𝑥 𝑥 ∈ 𝐴 ↔ ¬ 𝐴 = ∅) |
4 | 3 | bicomi 223 | 1 ⊢ (¬ 𝐴 = ∅ ↔ ∃𝑥 𝑥 ∈ 𝐴) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 ↔ wb 205 ∀wal 1540 = wceq 1542 ∃wex 1782 ∈ wcel 2107 ∅c0 4323 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1798 ax-4 1812 ax-5 1914 ax-6 1972 ax-7 2012 ax-9 2117 ax-ext 2704 |
This theorem depends on definitions: df-bi 206 df-an 398 df-tru 1545 df-fal 1555 df-ex 1783 df-sb 2069 df-clab 2711 df-cleq 2725 df-dif 3952 df-nul 4324 |
This theorem is referenced by: n0 4347 ralidmOLD 4516 falseral0 4520 snprc 4722 pwpw0 4817 sssn 4830 pwsnOLD 4902 uni0b 4938 disjor 5129 rnep 5927 isomin 7334 mpoxneldm 8197 mpoxopynvov0g 8199 mpoxopxnop0 8200 erdisj 8755 ixpprc 8913 sucdom2OLD 9082 domunsn 9127 sucdom2 9206 isinf 9260 isinfOLD 9261 nfielex 9273 enp1iOLD 9280 xpfiOLD 9318 scottex 9880 acndom 10046 axcclem 10452 axpowndlem3 10594 canthp1lem1 10647 isumltss 15794 pf1rcl 21868 ppttop 22510 ntreq0 22581 txindis 23138 txconn 23193 fmfnfm 23462 ptcmplem2 23557 ptcmplem3 23558 bddmulibl 25356 g0wlk0 28909 wwlksnndef 29159 strlem1 31503 disjorf 31810 ddemeas 33234 tgoldbachgt 33675 bnj1143 33801 prv1n 34422 pibt2 36298 poimirlem25 36513 poimirlem27 36515 ineleq 37223 eqvreldisj 37484 grucollcld 43019 fnchoice 43713 founiiun0 43888 nzerooringczr 46970 mo0sn 47500 map0cor 47521 |
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