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Mirrors > Home > MPE Home > Th. List > nnullss | Structured version Visualization version GIF version |
Description: A nonempty class (even if proper) has a nonempty subset. (Contributed by NM, 23-Aug-2003.) |
Ref | Expression |
---|---|
nnullss | ⊢ (𝐴 ≠ ∅ → ∃𝑥(𝑥 ⊆ 𝐴 ∧ 𝑥 ≠ ∅)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | n0 3890 | . 2 ⊢ (𝐴 ≠ ∅ ↔ ∃𝑦 𝑦 ∈ 𝐴) | |
2 | vex 3176 | . . . . 5 ⊢ 𝑦 ∈ V | |
3 | 2 | snss 4259 | . . . 4 ⊢ (𝑦 ∈ 𝐴 ↔ {𝑦} ⊆ 𝐴) |
4 | 2 | snnz 4252 | . . . . 5 ⊢ {𝑦} ≠ ∅ |
5 | snex 4835 | . . . . . 6 ⊢ {𝑦} ∈ V | |
6 | sseq1 3589 | . . . . . . 7 ⊢ (𝑥 = {𝑦} → (𝑥 ⊆ 𝐴 ↔ {𝑦} ⊆ 𝐴)) | |
7 | neeq1 2844 | . . . . . . 7 ⊢ (𝑥 = {𝑦} → (𝑥 ≠ ∅ ↔ {𝑦} ≠ ∅)) | |
8 | 6, 7 | anbi12d 743 | . . . . . 6 ⊢ (𝑥 = {𝑦} → ((𝑥 ⊆ 𝐴 ∧ 𝑥 ≠ ∅) ↔ ({𝑦} ⊆ 𝐴 ∧ {𝑦} ≠ ∅))) |
9 | 5, 8 | spcev 3273 | . . . . 5 ⊢ (({𝑦} ⊆ 𝐴 ∧ {𝑦} ≠ ∅) → ∃𝑥(𝑥 ⊆ 𝐴 ∧ 𝑥 ≠ ∅)) |
10 | 4, 9 | mpan2 703 | . . . 4 ⊢ ({𝑦} ⊆ 𝐴 → ∃𝑥(𝑥 ⊆ 𝐴 ∧ 𝑥 ≠ ∅)) |
11 | 3, 10 | sylbi 206 | . . 3 ⊢ (𝑦 ∈ 𝐴 → ∃𝑥(𝑥 ⊆ 𝐴 ∧ 𝑥 ≠ ∅)) |
12 | 11 | exlimiv 1845 | . 2 ⊢ (∃𝑦 𝑦 ∈ 𝐴 → ∃𝑥(𝑥 ⊆ 𝐴 ∧ 𝑥 ≠ ∅)) |
13 | 1, 12 | sylbi 206 | 1 ⊢ (𝐴 ≠ ∅ → ∃𝑥(𝑥 ⊆ 𝐴 ∧ 𝑥 ≠ ∅)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 383 = wceq 1475 ∃wex 1695 ∈ wcel 1977 ≠ wne 2780 ⊆ wss 3540 ∅c0 3874 {csn 4125 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1713 ax-4 1728 ax-5 1827 ax-6 1875 ax-7 1922 ax-9 1986 ax-10 2006 ax-11 2021 ax-12 2034 ax-13 2234 ax-ext 2590 ax-sep 4709 ax-nul 4717 ax-pr 4833 |
This theorem depends on definitions: df-bi 196 df-or 384 df-an 385 df-3an 1033 df-tru 1478 df-ex 1696 df-nf 1701 df-sb 1868 df-clab 2597 df-cleq 2603 df-clel 2606 df-nfc 2740 df-ne 2782 df-v 3175 df-dif 3543 df-un 3545 df-in 3547 df-ss 3554 df-nul 3875 df-sn 4126 df-pr 4128 |
This theorem is referenced by: (None) |
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