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Mirrors > Home > MPE Home > Th. List > Mathboxes > en2pr | Structured version Visualization version GIF version |
Description: A class is equinumerous to ordinal two iff it is a pair of distinct sets. (Contributed by RP, 11-Oct-2023.) |
Ref | Expression |
---|---|
en2pr | ⊢ (𝐴 ≈ 2o ↔ ∃𝑥∃𝑦(𝐴 = {𝑥, 𝑦} ∧ 𝑥 ≠ 𝑦)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | en2 9339 | . . 3 ⊢ (𝐴 ≈ 2o → ∃𝑥∃𝑦 𝐴 = {𝑥, 𝑦}) | |
2 | 1 | pm4.71ri 560 | . 2 ⊢ (𝐴 ≈ 2o ↔ (∃𝑥∃𝑦 𝐴 = {𝑥, 𝑦} ∧ 𝐴 ≈ 2o)) |
3 | 19.41vv 1950 | . 2 ⊢ (∃𝑥∃𝑦(𝐴 = {𝑥, 𝑦} ∧ 𝐴 ≈ 2o) ↔ (∃𝑥∃𝑦 𝐴 = {𝑥, 𝑦} ∧ 𝐴 ≈ 2o)) | |
4 | breq1 5172 | . . . . 5 ⊢ (𝐴 = {𝑥, 𝑦} → (𝐴 ≈ 2o ↔ {𝑥, 𝑦} ≈ 2o)) | |
5 | pr2ne 10069 | . . . . . 6 ⊢ ((𝑥 ∈ V ∧ 𝑦 ∈ V) → ({𝑥, 𝑦} ≈ 2o ↔ 𝑥 ≠ 𝑦)) | |
6 | 5 | el2v 3490 | . . . . 5 ⊢ ({𝑥, 𝑦} ≈ 2o ↔ 𝑥 ≠ 𝑦) |
7 | 4, 6 | bitrdi 287 | . . . 4 ⊢ (𝐴 = {𝑥, 𝑦} → (𝐴 ≈ 2o ↔ 𝑥 ≠ 𝑦)) |
8 | 7 | pm5.32i 574 | . . 3 ⊢ ((𝐴 = {𝑥, 𝑦} ∧ 𝐴 ≈ 2o) ↔ (𝐴 = {𝑥, 𝑦} ∧ 𝑥 ≠ 𝑦)) |
9 | 8 | 2exbii 1847 | . 2 ⊢ (∃𝑥∃𝑦(𝐴 = {𝑥, 𝑦} ∧ 𝐴 ≈ 2o) ↔ ∃𝑥∃𝑦(𝐴 = {𝑥, 𝑦} ∧ 𝑥 ≠ 𝑦)) |
10 | 2, 3, 9 | 3bitr2i 299 | 1 ⊢ (𝐴 ≈ 2o ↔ ∃𝑥∃𝑦(𝐴 = {𝑥, 𝑦} ∧ 𝑥 ≠ 𝑦)) |
Colors of variables: wff setvar class |
Syntax hints: ↔ wb 206 ∧ wa 395 = wceq 1537 ∃wex 1777 ≠ wne 2942 Vcvv 3482 {cpr 4650 class class class wbr 5169 2oc2o 8512 ≈ cen 8996 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1793 ax-4 1807 ax-5 1909 ax-6 1967 ax-7 2007 ax-8 2105 ax-9 2113 ax-10 2136 ax-11 2153 ax-12 2173 ax-ext 2705 ax-sep 5320 ax-nul 5327 ax-pr 5450 |
This theorem depends on definitions: df-bi 207 df-an 396 df-or 847 df-3or 1088 df-3an 1089 df-tru 1540 df-fal 1550 df-ex 1778 df-nf 1782 df-sb 2065 df-mo 2537 df-eu 2566 df-clab 2712 df-cleq 2726 df-clel 2813 df-ne 2943 df-ral 3064 df-rex 3073 df-reu 3384 df-rab 3439 df-v 3484 df-dif 3973 df-un 3975 df-in 3977 df-ss 3987 df-pss 3990 df-nul 4348 df-if 4549 df-pw 4624 df-sn 4649 df-pr 4651 df-op 4655 df-uni 4932 df-br 5170 df-opab 5232 df-tr 5287 df-id 5597 df-eprel 5603 df-po 5611 df-so 5612 df-fr 5654 df-we 5656 df-xp 5705 df-rel 5706 df-cnv 5707 df-co 5708 df-dm 5709 df-rn 5710 df-res 5711 df-ima 5712 df-ord 6397 df-on 6398 df-suc 6400 df-iota 6524 df-fun 6574 df-fn 6575 df-f 6576 df-f1 6577 df-fo 6578 df-f1o 6579 df-fv 6580 df-1o 8518 df-2o 8519 df-en 9000 |
This theorem is referenced by: (None) |
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