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Theorem 3eltr4d 2364
Description: Substitution of equal classes into membership relation. (Contributed by Mario Carneiro, 6-Jan-2017.)
Hypotheses
Ref Expression
3eltr4d.1  |-  ( ph  ->  A  e.  B )
3eltr4d.2  |-  ( ph  ->  C  =  A )
3eltr4d.3  |-  ( ph  ->  D  =  B )
Assertion
Ref Expression
3eltr4d  |-  ( ph  ->  C  e.  D )

Proof of Theorem 3eltr4d
StepHypRef Expression
1 3eltr4d.2 . 2  |-  ( ph  ->  C  =  A )
2 3eltr4d.1 . . 3  |-  ( ph  ->  A  e.  B )
3 3eltr4d.3 . . 3  |-  ( ph  ->  D  =  B )
42, 3eleqtrrd 2360 . 2  |-  ( ph  ->  A  e.  D )
51, 4eqeltrd 2357 1  |-  ( ph  ->  C  e.  D )
Colors of variables: wff set class
Syntax hints:    -> wi 4    = wceq 1623    e. wcel 1684
This theorem is referenced by:  issubc3  13723  xpccatid  13962
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1533  ax-5 1544  ax-17 1603  ax-9 1635  ax-8 1643  ax-11 1715  ax-ext 2264
This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1529  df-cleq 2276  df-clel 2279
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