![]() |
Metamath Proof Explorer |
< Previous
Next >
Nearby theorems |
|
Mirrors > Home > MPE Home > Th. List > sdom1 | Structured version Visualization version GIF version |
Description: A set has less than one member iff it is empty. (Contributed by Stefan O'Rear, 28-Oct-2014.) Avoid ax-pow 5365, ax-un 7740. (Revised by BTernaryTau, 12-Dec-2024.) |
Ref | Expression |
---|---|
sdom1 | ⊢ (𝐴 ≺ 1o ↔ 𝐴 = ∅) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df1o2 8494 | . . . . . . 7 ⊢ 1o = {∅} | |
2 | 1 | breq2i 5156 | . . . . . 6 ⊢ (𝐴 ≼ 1o ↔ 𝐴 ≼ {∅}) |
3 | brdomi 8979 | . . . . . . 7 ⊢ (𝐴 ≼ {∅} → ∃𝑓 𝑓:𝐴–1-1→{∅}) | |
4 | f1cdmsn 7291 | . . . . . . . . . 10 ⊢ ((𝑓:𝐴–1-1→{∅} ∧ 𝐴 ≠ ∅) → ∃𝑥 𝐴 = {𝑥}) | |
5 | vex 3475 | . . . . . . . . . . . . 13 ⊢ 𝑥 ∈ V | |
6 | 5 | ensn1 9042 | . . . . . . . . . . . 12 ⊢ {𝑥} ≈ 1o |
7 | breq1 5151 | . . . . . . . . . . . 12 ⊢ (𝐴 = {𝑥} → (𝐴 ≈ 1o ↔ {𝑥} ≈ 1o)) | |
8 | 6, 7 | mpbiri 258 | . . . . . . . . . . 11 ⊢ (𝐴 = {𝑥} → 𝐴 ≈ 1o) |
9 | 8 | exlimiv 1926 | . . . . . . . . . 10 ⊢ (∃𝑥 𝐴 = {𝑥} → 𝐴 ≈ 1o) |
10 | 4, 9 | syl 17 | . . . . . . . . 9 ⊢ ((𝑓:𝐴–1-1→{∅} ∧ 𝐴 ≠ ∅) → 𝐴 ≈ 1o) |
11 | 10 | expcom 413 | . . . . . . . 8 ⊢ (𝐴 ≠ ∅ → (𝑓:𝐴–1-1→{∅} → 𝐴 ≈ 1o)) |
12 | 11 | exlimdv 1929 | . . . . . . 7 ⊢ (𝐴 ≠ ∅ → (∃𝑓 𝑓:𝐴–1-1→{∅} → 𝐴 ≈ 1o)) |
13 | 3, 12 | syl5 34 | . . . . . 6 ⊢ (𝐴 ≠ ∅ → (𝐴 ≼ {∅} → 𝐴 ≈ 1o)) |
14 | 2, 13 | biimtrid 241 | . . . . 5 ⊢ (𝐴 ≠ ∅ → (𝐴 ≼ 1o → 𝐴 ≈ 1o)) |
15 | iman 401 | . . . . 5 ⊢ ((𝐴 ≼ 1o → 𝐴 ≈ 1o) ↔ ¬ (𝐴 ≼ 1o ∧ ¬ 𝐴 ≈ 1o)) | |
16 | 14, 15 | sylib 217 | . . . 4 ⊢ (𝐴 ≠ ∅ → ¬ (𝐴 ≼ 1o ∧ ¬ 𝐴 ≈ 1o)) |
17 | brsdom 8996 | . . . 4 ⊢ (𝐴 ≺ 1o ↔ (𝐴 ≼ 1o ∧ ¬ 𝐴 ≈ 1o)) | |
18 | 16, 17 | sylnibr 329 | . . 3 ⊢ (𝐴 ≠ ∅ → ¬ 𝐴 ≺ 1o) |
19 | 18 | necon4ai 2969 | . 2 ⊢ (𝐴 ≺ 1o → 𝐴 = ∅) |
20 | 1n0 8509 | . . . 4 ⊢ 1o ≠ ∅ | |
21 | 1oex 8497 | . . . . 5 ⊢ 1o ∈ V | |
22 | 21 | 0sdom 9132 | . . . 4 ⊢ (∅ ≺ 1o ↔ 1o ≠ ∅) |
23 | 20, 22 | mpbir 230 | . . 3 ⊢ ∅ ≺ 1o |
24 | breq1 5151 | . . 3 ⊢ (𝐴 = ∅ → (𝐴 ≺ 1o ↔ ∅ ≺ 1o)) | |
25 | 23, 24 | mpbiri 258 | . 2 ⊢ (𝐴 = ∅ → 𝐴 ≺ 1o) |
26 | 19, 25 | impbii 208 | 1 ⊢ (𝐴 ≺ 1o ↔ 𝐴 = ∅) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ↔ wb 205 ∧ wa 395 = wceq 1534 ∃wex 1774 ≠ wne 2937 ∅c0 4323 {csn 4629 class class class wbr 5148 –1-1→wf1 6545 1oc1o 8480 ≈ cen 8961 ≼ cdom 8962 ≺ csdm 8963 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1790 ax-4 1804 ax-5 1906 ax-6 1964 ax-7 2004 ax-8 2101 ax-9 2109 ax-10 2130 ax-11 2147 ax-12 2167 ax-ext 2699 ax-sep 5299 ax-nul 5306 ax-pr 5429 |
This theorem depends on definitions: df-bi 206 df-an 396 df-or 847 df-3an 1087 df-tru 1537 df-fal 1547 df-ex 1775 df-nf 1779 df-sb 2061 df-mo 2530 df-eu 2559 df-clab 2706 df-cleq 2720 df-clel 2806 df-ne 2938 df-ral 3059 df-rex 3068 df-rab 3430 df-v 3473 df-dif 3950 df-un 3952 df-in 3954 df-ss 3964 df-nul 4324 df-if 4530 df-sn 4630 df-pr 4632 df-op 4636 df-uni 4909 df-br 5149 df-opab 5211 df-id 5576 df-xp 5684 df-rel 5685 df-cnv 5686 df-co 5687 df-dm 5688 df-rn 5689 df-suc 6375 df-iota 6500 df-fun 6550 df-fn 6551 df-f 6552 df-f1 6553 df-fo 6554 df-f1o 6555 df-fv 6556 df-1o 8487 df-en 8965 df-dom 8966 df-sdom 8967 |
This theorem is referenced by: modom 9269 frgpcyg 21507 |
Copyright terms: Public domain | W3C validator |