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Theorem dfss5OLD 3803
 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 3801 . 2 (𝐴𝐵 ↔ (𝐵𝐴) = 𝐴)
2 eqcom 2628 . 2 ((𝐵𝐴) = 𝐴𝐴 = (𝐵𝐴))
31, 2bitri 264 1 (𝐴𝐵𝐴 = (𝐵𝐴))
 Colors of variables: wff setvar class Syntax hints:   ↔ wb 196   = wceq 1480   ∩ cin 3559   ⊆ wss 3560 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1836  ax-6 1885  ax-7 1932  ax-9 1996  ax-10 2016  ax-11 2031  ax-12 2044  ax-13 2245  ax-ext 2601 This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1483  df-ex 1702  df-nf 1707  df-sb 1878  df-clab 2608  df-cleq 2614  df-clel 2617  df-nfc 2750  df-v 3192  df-in 3567  df-ss 3574 This theorem is referenced by: (None)
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