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Theorem cnvsym 5412
Description: Two ways of saying a relation is symmetric. Similar to definition of symmetry in [Schechter] p. 51. (Contributed by NM, 28-Dec-1996.) (Proof shortened by Andrew Salmon, 27-Aug-2011.)
Assertion
Ref Expression
cnvsym (𝑅𝑅 ↔ ∀𝑥𝑦(𝑥𝑅𝑦𝑦𝑅𝑥))
Distinct variable group:   𝑥,𝑦,𝑅

Proof of Theorem cnvsym
StepHypRef Expression
1 alcom 2022 . 2 (∀𝑦𝑥(⟨𝑦, 𝑥⟩ ∈ 𝑅 → ⟨𝑦, 𝑥⟩ ∈ 𝑅) ↔ ∀𝑥𝑦(⟨𝑦, 𝑥⟩ ∈ 𝑅 → ⟨𝑦, 𝑥⟩ ∈ 𝑅))
2 relcnv 5405 . . 3 Rel 𝑅
3 ssrel 5116 . . 3 (Rel 𝑅 → (𝑅𝑅 ↔ ∀𝑦𝑥(⟨𝑦, 𝑥⟩ ∈ 𝑅 → ⟨𝑦, 𝑥⟩ ∈ 𝑅)))
42, 3ax-mp 5 . 2 (𝑅𝑅 ↔ ∀𝑦𝑥(⟨𝑦, 𝑥⟩ ∈ 𝑅 → ⟨𝑦, 𝑥⟩ ∈ 𝑅))
5 vex 3171 . . . . . 6 𝑦 ∈ V
6 vex 3171 . . . . . 6 𝑥 ∈ V
75, 6brcnv 5211 . . . . 5 (𝑦𝑅𝑥𝑥𝑅𝑦)
8 df-br 4574 . . . . 5 (𝑦𝑅𝑥 ↔ ⟨𝑦, 𝑥⟩ ∈ 𝑅)
97, 8bitr3i 264 . . . 4 (𝑥𝑅𝑦 ↔ ⟨𝑦, 𝑥⟩ ∈ 𝑅)
10 df-br 4574 . . . 4 (𝑦𝑅𝑥 ↔ ⟨𝑦, 𝑥⟩ ∈ 𝑅)
119, 10imbi12i 338 . . 3 ((𝑥𝑅𝑦𝑦𝑅𝑥) ↔ (⟨𝑦, 𝑥⟩ ∈ 𝑅 → ⟨𝑦, 𝑥⟩ ∈ 𝑅))
12112albii 1736 . 2 (∀𝑥𝑦(𝑥𝑅𝑦𝑦𝑅𝑥) ↔ ∀𝑥𝑦(⟨𝑦, 𝑥⟩ ∈ 𝑅 → ⟨𝑦, 𝑥⟩ ∈ 𝑅))
131, 4, 123bitr4i 290 1 (𝑅𝑅 ↔ ∀𝑥𝑦(𝑥𝑅𝑦𝑦𝑅𝑥))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 194  wal 1472  wcel 1975  wss 3535  cop 4126   class class class wbr 4573  ccnv 5023  Rel wrel 5029
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1711  ax-4 1726  ax-5 1825  ax-6 1873  ax-7 1920  ax-9 1984  ax-10 2004  ax-11 2019  ax-12 2031  ax-13 2228  ax-ext 2585  ax-sep 4699  ax-nul 4708  ax-pr 4824
This theorem depends on definitions:  df-bi 195  df-or 383  df-an 384  df-3an 1032  df-tru 1477  df-ex 1695  df-nf 1700  df-sb 1866  df-eu 2457  df-mo 2458  df-clab 2592  df-cleq 2598  df-clel 2601  df-nfc 2735  df-ral 2896  df-rex 2897  df-rab 2900  df-v 3170  df-dif 3538  df-un 3540  df-in 3542  df-ss 3549  df-nul 3870  df-if 4032  df-sn 4121  df-pr 4123  df-op 4127  df-br 4574  df-opab 4634  df-xp 5030  df-rel 5031  df-cnv 5032
This theorem is referenced by:  dfer2  7603
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