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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.) |
Ref | Expression |
---|---|
neq0 | ⊢ (¬ 𝐴 = ∅ ↔ ∃𝑥 𝑥 ∈ 𝐴) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nfcv 2977 | . 2 ⊢ Ⅎ𝑥𝐴 | |
2 | 1 | neq0f 4306 | 1 ⊢ (¬ 𝐴 = ∅ ↔ ∃𝑥 𝑥 ∈ 𝐴) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 ↔ wb 208 = wceq 1537 ∃wex 1780 ∈ wcel 2114 ∅c0 4291 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2116 ax-9 2124 ax-11 2161 ax-12 2177 ax-ext 2793 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 df-clab 2800 df-cleq 2814 df-clel 2893 df-nfc 2963 df-dif 3939 df-nul 4292 |
This theorem is referenced by: ralidm 4455 falseral0 4459 snprc 4653 pwpw0 4746 sssn 4759 pwsnOLD 4831 uni0b 4864 disjor 5046 rnep 5797 isomin 7090 mpoxneldm 7878 mpoxopynvov0g 7880 mpoxopxnop0 7881 erdisj 8341 ixpprc 8483 domunsn 8667 sucdom2 8714 isinf 8731 nfielex 8747 enp1i 8753 xpfi 8789 scottex 9314 acndom 9477 axcclem 9879 axpowndlem3 10021 canthp1lem1 10074 isumltss 15203 pf1rcl 20512 ppttop 21615 ntreq0 21685 txindis 22242 txconn 22297 fmfnfm 22566 ptcmplem2 22661 ptcmplem3 22662 bddmulibl 24439 g0wlk0 27433 wwlksnndef 27683 strlem1 30027 disjorf 30329 ddemeas 31495 tgoldbachgt 31934 bnj1143 32062 prv1n 32678 pibt2 34701 poimirlem25 34932 poimirlem27 34934 ineleq 35623 eqvreldisj 35864 grucollcld 40616 fnchoice 41306 founiiun0 41471 nzerooringczr 44363 |
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