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Mirrors > Home > MPE Home > Th. List > nelsn | Structured version Visualization version GIF version |
Description: If a class is not equal to the class in a singleton, then it is not in the singleton. (Contributed by Glauco Siliprandi, 17-Aug-2020.) (Proof shortened by BJ, 4-May-2021.) |
Ref | Expression |
---|---|
nelsn | ⊢ (𝐴 ≠ 𝐵 → ¬ 𝐴 ∈ {𝐵}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | elsni 4142 | . 2 ⊢ (𝐴 ∈ {𝐵} → 𝐴 = 𝐵) | |
2 | 1 | necon3ai 2807 | 1 ⊢ (𝐴 ≠ 𝐵 → ¬ 𝐴 ∈ {𝐵}) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ∈ wcel 1977 ≠ wne 2780 {csn 4125 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1713 ax-4 1728 ax-5 1827 ax-6 1875 ax-7 1922 ax-10 2006 ax-11 2021 ax-12 2034 ax-13 2234 ax-ext 2590 |
This theorem depends on definitions: df-bi 196 df-or 384 df-an 385 df-tru 1478 df-ex 1696 df-nf 1701 df-sb 1868 df-clab 2597 df-cleq 2603 df-clel 2606 df-nfc 2740 df-ne 2782 df-v 3175 df-sn 4126 |
This theorem is referenced by: fvunsn 6350 nnoddn2prmb 15356 lbsextlem4 18982 obslbs 19893 vdgr1b 26431 submateqlem1 29201 submateqlem2 29202 qqhval2 29354 derangsn 30406 clsk3nimkb 37358 clsk1indlem1 37363 disjf1o 38373 fperdvper 38808 dvnmul 38833 wallispi 38963 etransc 39176 gsumge0cl 39264 meadjiunlem 39358 hspmbllem2 39517 upgrres1 40532 |
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