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Mirrors > Home > MPE Home > Th. List > xpnz | Structured version Visualization version GIF version |
Description: The Cartesian product of nonempty classes is nonempty. (Variation of a theorem contributed by Raph Levien, 30-Jun-2006.) (Contributed by NM, 30-Jun-2006.) |
Ref | Expression |
---|---|
xpnz | ⊢ ((𝐴 ≠ ∅ ∧ 𝐵 ≠ ∅) ↔ (𝐴 × 𝐵) ≠ ∅) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | n0 4310 | . . . . 5 ⊢ (𝐴 ≠ ∅ ↔ ∃𝑥 𝑥 ∈ 𝐴) | |
2 | n0 4310 | . . . . 5 ⊢ (𝐵 ≠ ∅ ↔ ∃𝑦 𝑦 ∈ 𝐵) | |
3 | 1, 2 | anbi12i 628 | . . . 4 ⊢ ((𝐴 ≠ ∅ ∧ 𝐵 ≠ ∅) ↔ (∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑦 𝑦 ∈ 𝐵)) |
4 | exdistrv 1960 | . . . 4 ⊢ (∃𝑥∃𝑦(𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵) ↔ (∃𝑥 𝑥 ∈ 𝐴 ∧ ∃𝑦 𝑦 ∈ 𝐵)) | |
5 | 3, 4 | bitr4i 278 | . . 3 ⊢ ((𝐴 ≠ ∅ ∧ 𝐵 ≠ ∅) ↔ ∃𝑥∃𝑦(𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵)) |
6 | opex 5425 | . . . . . 6 ⊢ ⟨𝑥, 𝑦⟩ ∈ V | |
7 | eleq1 2822 | . . . . . . 7 ⊢ (𝑧 = ⟨𝑥, 𝑦⟩ → (𝑧 ∈ (𝐴 × 𝐵) ↔ ⟨𝑥, 𝑦⟩ ∈ (𝐴 × 𝐵))) | |
8 | opelxp 5673 | . . . . . . 7 ⊢ (⟨𝑥, 𝑦⟩ ∈ (𝐴 × 𝐵) ↔ (𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵)) | |
9 | 7, 8 | bitrdi 287 | . . . . . 6 ⊢ (𝑧 = ⟨𝑥, 𝑦⟩ → (𝑧 ∈ (𝐴 × 𝐵) ↔ (𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵))) |
10 | 6, 9 | spcev 3567 | . . . . 5 ⊢ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵) → ∃𝑧 𝑧 ∈ (𝐴 × 𝐵)) |
11 | n0 4310 | . . . . 5 ⊢ ((𝐴 × 𝐵) ≠ ∅ ↔ ∃𝑧 𝑧 ∈ (𝐴 × 𝐵)) | |
12 | 10, 11 | sylibr 233 | . . . 4 ⊢ ((𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵) → (𝐴 × 𝐵) ≠ ∅) |
13 | 12 | exlimivv 1936 | . . 3 ⊢ (∃𝑥∃𝑦(𝑥 ∈ 𝐴 ∧ 𝑦 ∈ 𝐵) → (𝐴 × 𝐵) ≠ ∅) |
14 | 5, 13 | sylbi 216 | . 2 ⊢ ((𝐴 ≠ ∅ ∧ 𝐵 ≠ ∅) → (𝐴 × 𝐵) ≠ ∅) |
15 | xpeq1 5651 | . . . . 5 ⊢ (𝐴 = ∅ → (𝐴 × 𝐵) = (∅ × 𝐵)) | |
16 | 0xp 5734 | . . . . 5 ⊢ (∅ × 𝐵) = ∅ | |
17 | 15, 16 | eqtrdi 2789 | . . . 4 ⊢ (𝐴 = ∅ → (𝐴 × 𝐵) = ∅) |
18 | 17 | necon3i 2973 | . . 3 ⊢ ((𝐴 × 𝐵) ≠ ∅ → 𝐴 ≠ ∅) |
19 | xpeq2 5658 | . . . . 5 ⊢ (𝐵 = ∅ → (𝐴 × 𝐵) = (𝐴 × ∅)) | |
20 | xp0 6114 | . . . . 5 ⊢ (𝐴 × ∅) = ∅ | |
21 | 19, 20 | eqtrdi 2789 | . . . 4 ⊢ (𝐵 = ∅ → (𝐴 × 𝐵) = ∅) |
22 | 21 | necon3i 2973 | . . 3 ⊢ ((𝐴 × 𝐵) ≠ ∅ → 𝐵 ≠ ∅) |
23 | 18, 22 | jca 513 | . 2 ⊢ ((𝐴 × 𝐵) ≠ ∅ → (𝐴 ≠ ∅ ∧ 𝐵 ≠ ∅)) |
24 | 14, 23 | impbii 208 | 1 ⊢ ((𝐴 ≠ ∅ ∧ 𝐵 ≠ ∅) ↔ (𝐴 × 𝐵) ≠ ∅) |
Colors of variables: wff setvar class |
Syntax hints: ↔ wb 205 ∧ wa 397 = wceq 1542 ∃wex 1782 ∈ wcel 2107 ≠ wne 2940 ∅c0 4286 ⟨cop 4596 × cxp 5635 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1798 ax-4 1812 ax-5 1914 ax-6 1972 ax-7 2012 ax-8 2109 ax-9 2117 ax-10 2138 ax-11 2155 ax-12 2172 ax-ext 2704 ax-sep 5260 ax-nul 5267 ax-pr 5388 |
This theorem depends on definitions: df-bi 206 df-an 398 df-or 847 df-3an 1090 df-tru 1545 df-fal 1555 df-ex 1783 df-nf 1787 df-sb 2069 df-clab 2711 df-cleq 2725 df-clel 2811 df-ne 2941 df-ral 3062 df-rex 3071 df-rab 3407 df-v 3449 df-dif 3917 df-un 3919 df-in 3921 df-ss 3931 df-nul 4287 df-if 4491 df-sn 4591 df-pr 4593 df-op 4597 df-br 5110 df-opab 5172 df-xp 5643 df-rel 5644 df-cnv 5645 |
This theorem is referenced by: xpeq0 6116 ssxpb 6130 xp11 6131 unixpid 6240 xpexr2 7860 frxp 8062 xpfir 9216 axcc2lem 10380 axdc4lem 10399 mamufacex 21761 txindis 23008 2ndimaxp 31616 bj-xpnzex 35480 bj-1upln0 35530 bj-2upln1upl 35545 dibn0 39666 |
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