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Mirrors > Home > MPE Home > Th. List > prnesn | Structured version Visualization version GIF version |
Description: A proper unordered pair is not a (proper or improper) singleton. (Contributed by AV, 13-Jun-2022.) |
Ref | Expression |
---|---|
prnesn | ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐴 ≠ 𝐵) → {𝐴, 𝐵} ≠ {𝐶}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqtr3 2801 | . . . 4 ⊢ ((𝐴 = 𝐶 ∧ 𝐵 = 𝐶) → 𝐴 = 𝐵) | |
2 | 1 | necon3ai 2992 | . . 3 ⊢ (𝐴 ≠ 𝐵 → ¬ (𝐴 = 𝐶 ∧ 𝐵 = 𝐶)) |
3 | 2 | 3ad2ant3 1115 | . 2 ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐴 ≠ 𝐵) → ¬ (𝐴 = 𝐶 ∧ 𝐵 = 𝐶)) |
4 | elex 3433 | . . . . 5 ⊢ (𝐴 ∈ 𝑉 → 𝐴 ∈ V) | |
5 | 4 | 3ad2ant1 1113 | . . . 4 ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐴 ≠ 𝐵) → 𝐴 ∈ V) |
6 | elex 3433 | . . . . 5 ⊢ (𝐵 ∈ 𝑊 → 𝐵 ∈ V) | |
7 | 6 | 3ad2ant2 1114 | . . . 4 ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐴 ≠ 𝐵) → 𝐵 ∈ V) |
8 | 5, 7 | preqsnd 4663 | . . 3 ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐴 ≠ 𝐵) → ({𝐴, 𝐵} = {𝐶} ↔ (𝐴 = 𝐶 ∧ 𝐵 = 𝐶))) |
9 | 8 | necon3abid 3003 | . 2 ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐴 ≠ 𝐵) → ({𝐴, 𝐵} ≠ {𝐶} ↔ ¬ (𝐴 = 𝐶 ∧ 𝐵 = 𝐶))) |
10 | 3, 9 | mpbird 249 | 1 ⊢ ((𝐴 ∈ 𝑉 ∧ 𝐵 ∈ 𝑊 ∧ 𝐴 ≠ 𝐵) → {𝐴, 𝐵} ≠ {𝐶}) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ∧ wa 387 ∧ w3a 1068 = wceq 1507 ∈ wcel 2050 ≠ wne 2967 Vcvv 3415 {csn 4441 {cpr 4443 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1758 ax-4 1772 ax-5 1869 ax-6 1928 ax-7 1965 ax-8 2052 ax-9 2059 ax-10 2079 ax-11 2093 ax-12 2106 ax-ext 2750 |
This theorem depends on definitions: df-bi 199 df-an 388 df-or 834 df-3an 1070 df-tru 1510 df-ex 1743 df-nf 1747 df-sb 2016 df-clab 2759 df-cleq 2771 df-clel 2846 df-nfc 2918 df-ne 2968 df-v 3417 df-dif 3832 df-un 3834 df-nul 4179 df-sn 4442 df-pr 4444 |
This theorem is referenced by: prneprprc 4665 |
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