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Mirrors > Home > ILE Home > Th. List > eqss | GIF version |
Description: The subclass relationship is antisymmetric. Compare Theorem 4 of [Suppes] p. 22. (Contributed by NM, 5-Aug-1993.) |
Ref | Expression |
---|---|
eqss | ⊢ (𝐴 = 𝐵 ↔ (𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | albiim 1464 | . 2 ⊢ (∀𝑥(𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵) ↔ (∀𝑥(𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐵) ∧ ∀𝑥(𝑥 ∈ 𝐵 → 𝑥 ∈ 𝐴))) | |
2 | dfcleq 2134 | . 2 ⊢ (𝐴 = 𝐵 ↔ ∀𝑥(𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵)) | |
3 | dfss2 3091 | . . 3 ⊢ (𝐴 ⊆ 𝐵 ↔ ∀𝑥(𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐵)) | |
4 | dfss2 3091 | . . 3 ⊢ (𝐵 ⊆ 𝐴 ↔ ∀𝑥(𝑥 ∈ 𝐵 → 𝑥 ∈ 𝐴)) | |
5 | 3, 4 | anbi12i 456 | . 2 ⊢ ((𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴) ↔ (∀𝑥(𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐵) ∧ ∀𝑥(𝑥 ∈ 𝐵 → 𝑥 ∈ 𝐴))) |
6 | 1, 2, 5 | 3bitr4i 211 | 1 ⊢ (𝐴 = 𝐵 ↔ (𝐴 ⊆ 𝐵 ∧ 𝐵 ⊆ 𝐴)) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 103 ↔ wb 104 ∀wal 1330 = wceq 1332 ∈ wcel 1481 ⊆ wss 3076 |
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-5 1424 ax-7 1425 ax-gen 1426 ax-ie1 1470 ax-ie2 1471 ax-8 1483 ax-11 1485 ax-4 1488 ax-17 1507 ax-i9 1511 ax-ial 1515 ax-i5r 1516 ax-ext 2122 |
This theorem depends on definitions: df-bi 116 df-nf 1438 df-sb 1737 df-clab 2127 df-cleq 2133 df-clel 2136 df-in 3082 df-ss 3089 |
This theorem is referenced by: eqssi 3118 eqssd 3119 sseq1 3125 sseq2 3126 eqimss 3156 ssrabeq 3188 uneqin 3332 ss0b 3407 vss 3415 sssnm 3689 unidif 3776 ssunieq 3777 iuneq1 3834 iuneq2 3837 iunxdif2 3869 ssext 4151 pweqb 4153 eqopab2b 4209 pwunim 4216 soeq2 4246 iunpw 4409 ordunisuc2r 4438 tfi 4504 eqrel 4636 eqrelrel 4648 coeq1 4704 coeq2 4705 cnveq 4721 dmeq 4747 relssres 4865 xp11m 4985 xpcanm 4986 xpcan2m 4987 ssrnres 4989 fnres 5247 eqfnfv3 5528 fneqeql2 5537 fconst4m 5648 f1imaeq 5684 eqoprab2b 5837 fo1stresm 6067 fo2ndresm 6068 nnacan 6416 nnmcan 6423 ixpeq2 6614 sbthlemi3 6855 isprm2 11834 bastop1 12291 epttop 12298 opnneiid 12372 cnntr 12433 metequiv 12703 bj-sseq 13170 bdeq0 13236 bdvsn 13243 bdop 13244 bdeqsuc 13250 bj-om 13306 |
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