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Mirrors > Home > ILE Home > Th. List > un0 | GIF version |
Description: The union of a class with the empty set is itself. Theorem 24 of [Suppes] p. 27. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
un0 | ⊢ (𝐴 ∪ ∅) = 𝐴 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | noel 3367 | . . . 4 ⊢ ¬ 𝑥 ∈ ∅ | |
2 | 1 | biorfi 735 | . . 3 ⊢ (𝑥 ∈ 𝐴 ↔ (𝑥 ∈ 𝐴 ∨ 𝑥 ∈ ∅)) |
3 | 2 | bicomi 131 | . 2 ⊢ ((𝑥 ∈ 𝐴 ∨ 𝑥 ∈ ∅) ↔ 𝑥 ∈ 𝐴) |
4 | 3 | uneqri 3218 | 1 ⊢ (𝐴 ∪ ∅) = 𝐴 |
Colors of variables: wff set class |
Syntax hints: ∨ wo 697 = wceq 1331 ∈ wcel 1480 ∪ cun 3069 ∅c0 3363 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 603 ax-in2 604 ax-io 698 ax-5 1423 ax-7 1424 ax-gen 1425 ax-ie1 1469 ax-ie2 1470 ax-8 1482 ax-10 1483 ax-11 1484 ax-i12 1485 ax-bndl 1486 ax-4 1487 ax-17 1506 ax-i9 1510 ax-ial 1514 ax-i5r 1515 ax-ext 2121 |
This theorem depends on definitions: df-bi 116 df-tru 1334 df-nf 1437 df-sb 1736 df-clab 2126 df-cleq 2132 df-clel 2135 df-nfc 2270 df-v 2688 df-dif 3073 df-un 3075 df-nul 3364 |
This theorem is referenced by: un00 3409 disjssun 3426 difun2 3442 difdifdirss 3447 disjpr2 3587 prprc1 3631 diftpsn3 3661 iununir 3896 suc0 4333 sucprc 4334 fvun1 5487 fmptpr 5612 fvunsng 5614 fvsnun1 5617 fvsnun2 5618 fsnunfv 5621 fsnunres 5622 rdg0 6284 omv2 6361 unsnfidcex 6808 unfidisj 6810 undifdc 6812 ssfirab 6822 dju0en 7070 djuassen 7073 fzsuc2 9859 fseq1p1m1 9874 hashunlem 10550 ennnfonelem1 11920 setsresg 11997 setsslid 12009 exmid1stab 13195 |
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