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Mirrors > Home > MPE Home > Th. List > elpr2 | Structured version Visualization version GIF version |
Description: A member of an unordered pair of classes is one or the other of them. Exercise 1 of [TakeutiZaring] p. 15. (Contributed by NM, 14-Oct-2005.) (Proof shortened by JJ, 23-Jul-2021.) |
Ref | Expression |
---|---|
elpr2.1 | ⊢ 𝐵 ∈ V |
elpr2.2 | ⊢ 𝐶 ∈ V |
Ref | Expression |
---|---|
elpr2 | ⊢ (𝐴 ∈ {𝐵, 𝐶} ↔ (𝐴 = 𝐵 ∨ 𝐴 = 𝐶)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | elex 3512 | . 2 ⊢ (𝐴 ∈ {𝐵, 𝐶} → 𝐴 ∈ V) | |
2 | elpr2.1 | . . . 4 ⊢ 𝐵 ∈ V | |
3 | eleq1 2900 | . . . 4 ⊢ (𝐴 = 𝐵 → (𝐴 ∈ V ↔ 𝐵 ∈ V)) | |
4 | 2, 3 | mpbiri 260 | . . 3 ⊢ (𝐴 = 𝐵 → 𝐴 ∈ V) |
5 | elpr2.2 | . . . 4 ⊢ 𝐶 ∈ V | |
6 | eleq1 2900 | . . . 4 ⊢ (𝐴 = 𝐶 → (𝐴 ∈ V ↔ 𝐶 ∈ V)) | |
7 | 5, 6 | mpbiri 260 | . . 3 ⊢ (𝐴 = 𝐶 → 𝐴 ∈ V) |
8 | 4, 7 | jaoi 853 | . 2 ⊢ ((𝐴 = 𝐵 ∨ 𝐴 = 𝐶) → 𝐴 ∈ V) |
9 | elprg 4588 | . 2 ⊢ (𝐴 ∈ V → (𝐴 ∈ {𝐵, 𝐶} ↔ (𝐴 = 𝐵 ∨ 𝐴 = 𝐶))) | |
10 | 1, 8, 9 | pm5.21nii 382 | 1 ⊢ (𝐴 ∈ {𝐵, 𝐶} ↔ (𝐴 = 𝐵 ∨ 𝐴 = 𝐶)) |
Colors of variables: wff setvar class |
Syntax hints: ↔ wb 208 ∨ wo 843 = wceq 1537 ∈ wcel 2114 Vcvv 3494 {cpr 4569 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2161 ax-12 2177 ax-ext 2793 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 df-clab 2800 df-cleq 2814 df-clel 2893 df-nfc 2963 df-v 3496 df-un 3941 df-sn 4568 df-pr 4570 |
This theorem is referenced by: elopg 5358 elxr 12512 fprodex01 30541 nofv 33164 |
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