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Theorem dfss5OLD 3962
Description: Obsolete as of 22-Jul-2021. (Contributed by David Moews, 1-May-2017.) (New usage is discouraged.) (Proof modification is discouraged.)
Assertion
Ref Expression
dfss5OLD (𝐴𝐵𝐴 = (𝐵𝐴))

Proof of Theorem dfss5OLD
StepHypRef Expression
1 sseqin2 3960 . 2 (𝐴𝐵 ↔ (𝐵𝐴) = 𝐴)
2 eqcom 2767 . 2 ((𝐵𝐴) = 𝐴𝐴 = (𝐵𝐴))
31, 2bitri 264 1 (𝐴𝐵𝐴 = (𝐵𝐴))
Colors of variables: wff setvar class
Syntax hints:  wb 196   = wceq 1632  cin 3714  wss 3715
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1871  ax-4 1886  ax-5 1988  ax-6 2054  ax-7 2090  ax-9 2148  ax-10 2168  ax-11 2183  ax-12 2196  ax-13 2391  ax-ext 2740
This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-tru 1635  df-ex 1854  df-nf 1859  df-sb 2047  df-clab 2747  df-cleq 2753  df-clel 2756  df-nfc 2891  df-v 3342  df-in 3722  df-ss 3729
This theorem is referenced by: (None)
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