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Theorem 3eltr4i 2432
Description: Substitution of equal classes into membership relation. (Contributed by Mario Carneiro, 6-Jan-2017.)
Hypotheses
Ref Expression
3eltr4.1 A B
3eltr4.2 C = A
3eltr4.3 D = B
Assertion
Ref Expression
3eltr4i C D

Proof of Theorem 3eltr4i
StepHypRef Expression
1 3eltr4.2 . 2 C = A
2 3eltr4.1 . . 3 A B
3 3eltr4.3 . . 3 D = B
42, 3eleqtrri 2426 . 2 A D
51, 4eqeltri 2423 1 C D
Colors of variables: wff setvar class
Syntax hints:   = wceq 1642   wcel 1710
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-11 1746  ax-ext 2334
This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1542  df-cleq 2346  df-clel 2349
This theorem is referenced by: (None)
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