Intuitionistic Logic Explorer |
< Previous
Next >
Nearby theorems |
||
Mirrors > Home > ILE Home > Th. List > prprc1 | GIF version |
Description: A proper class vanishes in an unordered pair. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
prprc1 | ⊢ (¬ 𝐴 ∈ V → {𝐴, 𝐵} = {𝐵}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | snprc 3648 | . 2 ⊢ (¬ 𝐴 ∈ V ↔ {𝐴} = ∅) | |
2 | uneq1 3274 | . . 3 ⊢ ({𝐴} = ∅ → ({𝐴} ∪ {𝐵}) = (∅ ∪ {𝐵})) | |
3 | df-pr 3590 | . . 3 ⊢ {𝐴, 𝐵} = ({𝐴} ∪ {𝐵}) | |
4 | uncom 3271 | . . . 4 ⊢ (∅ ∪ {𝐵}) = ({𝐵} ∪ ∅) | |
5 | un0 3448 | . . . 4 ⊢ ({𝐵} ∪ ∅) = {𝐵} | |
6 | 4, 5 | eqtr2i 2192 | . . 3 ⊢ {𝐵} = (∅ ∪ {𝐵}) |
7 | 2, 3, 6 | 3eqtr4g 2228 | . 2 ⊢ ({𝐴} = ∅ → {𝐴, 𝐵} = {𝐵}) |
8 | 1, 7 | sylbi 120 | 1 ⊢ (¬ 𝐴 ∈ V → {𝐴, 𝐵} = {𝐵}) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 = wceq 1348 ∈ wcel 2141 Vcvv 2730 ∪ cun 3119 ∅c0 3414 {csn 3583 {cpr 3584 |
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 609 ax-in2 610 ax-io 704 ax-5 1440 ax-7 1441 ax-gen 1442 ax-ie1 1486 ax-ie2 1487 ax-8 1497 ax-10 1498 ax-11 1499 ax-i12 1500 ax-bndl 1502 ax-4 1503 ax-17 1519 ax-i9 1523 ax-ial 1527 ax-i5r 1528 ax-ext 2152 |
This theorem depends on definitions: df-bi 116 df-tru 1351 df-fal 1354 df-nf 1454 df-sb 1756 df-clab 2157 df-cleq 2163 df-clel 2166 df-nfc 2301 df-v 2732 df-dif 3123 df-un 3125 df-nul 3415 df-sn 3589 df-pr 3590 |
This theorem is referenced by: prprc2 3692 prprc 3693 |
Copyright terms: Public domain | W3C validator |