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Mirrors > Home > ILE Home > Th. List > sssnr | GIF version |
Description: Empty set and the singleton itself are subsets of a singleton. Concerning the converse, see exmidsssn 4188. (Contributed by Jim Kingdon, 10-Aug-2018.) |
Ref | Expression |
---|---|
sssnr | ⊢ ((𝐴 = ∅ ∨ 𝐴 = {𝐵}) → 𝐴 ⊆ {𝐵}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0ss 3453 | . . 3 ⊢ ∅ ⊆ {𝐵} | |
2 | sseq1 3170 | . . 3 ⊢ (𝐴 = ∅ → (𝐴 ⊆ {𝐵} ↔ ∅ ⊆ {𝐵})) | |
3 | 1, 2 | mpbiri 167 | . 2 ⊢ (𝐴 = ∅ → 𝐴 ⊆ {𝐵}) |
4 | eqimss 3201 | . 2 ⊢ (𝐴 = {𝐵} → 𝐴 ⊆ {𝐵}) | |
5 | 3, 4 | jaoi 711 | 1 ⊢ ((𝐴 = ∅ ∨ 𝐴 = {𝐵}) → 𝐴 ⊆ {𝐵}) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∨ wo 703 = wceq 1348 ⊆ wss 3121 ∅c0 3414 {csn 3583 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 609 ax-in2 610 ax-io 704 ax-5 1440 ax-7 1441 ax-gen 1442 ax-ie1 1486 ax-ie2 1487 ax-8 1497 ax-10 1498 ax-11 1499 ax-i12 1500 ax-bndl 1502 ax-4 1503 ax-17 1519 ax-i9 1523 ax-ial 1527 ax-i5r 1528 ax-ext 2152 |
This theorem depends on definitions: df-bi 116 df-tru 1351 df-nf 1454 df-sb 1756 df-clab 2157 df-cleq 2163 df-clel 2166 df-nfc 2301 df-v 2732 df-dif 3123 df-in 3127 df-ss 3134 df-nul 3415 |
This theorem is referenced by: pwsnss 3790 |
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