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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 2175. (Revised by GG, 28-Jun-2024.) |
Ref | Expression |
---|---|
neq0 | ⊢ (¬ 𝐴 = ∅ ↔ ∃𝑥 𝑥 ∈ 𝐴) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-ex 1777 | . . 3 ⊢ (∃𝑥 𝑥 ∈ 𝐴 ↔ ¬ ∀𝑥 ¬ 𝑥 ∈ 𝐴) | |
2 | eq0 4356 | . . 3 ⊢ (𝐴 = ∅ ↔ ∀𝑥 ¬ 𝑥 ∈ 𝐴) | |
3 | 1, 2 | xchbinxr 335 | . 2 ⊢ (∃𝑥 𝑥 ∈ 𝐴 ↔ ¬ 𝐴 = ∅) |
4 | 3 | bicomi 224 | 1 ⊢ (¬ 𝐴 = ∅ ↔ ∃𝑥 𝑥 ∈ 𝐴) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 ↔ wb 206 ∀wal 1535 = wceq 1537 ∃wex 1776 ∈ wcel 2106 ∅c0 4339 |
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-9 2116 ax-ext 2706 |
This theorem depends on definitions: df-bi 207 df-an 396 df-tru 1540 df-fal 1550 df-ex 1777 df-sb 2063 df-clab 2713 df-cleq 2727 df-dif 3966 df-nul 4340 |
This theorem is referenced by: n0 4359 falseral0 4522 snprc 4722 pwpw0 4818 sssn 4831 uni0b 4938 disjor 5130 rnep 5940 isomin 7357 mpoxneldm 8236 mpoxopynvov0g 8238 mpoxopxnop0 8239 erdisj 8798 ixpprc 8958 sucdom2OLD 9121 domunsn 9166 sucdom2 9241 isinf 9294 isinfOLD 9295 nfielex 9305 enp1iOLD 9312 xpfiOLD 9357 scottex 9923 acndom 10089 axcclem 10495 axpowndlem3 10637 canthp1lem1 10690 isumltss 15881 nzerooringczr 21509 pf1rcl 22369 ppttop 23030 ntreq0 23101 txindis 23658 txconn 23713 fmfnfm 23982 ptcmplem2 24077 ptcmplem3 24078 bddmulibl 25889 g0wlk0 29685 wwlksnndef 29935 strlem1 32279 disjorf 32599 ssdifidlprm 33466 1arithufdlem4 33555 ddemeas 34217 tgoldbachgt 34657 bnj1143 34783 prv1n 35416 pibt2 37400 poimirlem25 37632 poimirlem27 37634 ineleq 38336 eqvreldisj 38596 grucollcld 44256 fnchoice 44967 founiiun0 45133 mo0sn 48664 map0cor 48685 |
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