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Theorem 3eltr3d 2120
Description: Substitution of equal classes into membership relation. (Contributed by Mario Carneiro, 6-Jan-2017.)
Hypotheses
Ref Expression
3eltr3d.1 (𝜑𝐴𝐵)
3eltr3d.2 (𝜑𝐴 = 𝐶)
3eltr3d.3 (𝜑𝐵 = 𝐷)
Assertion
Ref Expression
3eltr3d (𝜑𝐶𝐷)

Proof of Theorem 3eltr3d
StepHypRef Expression
1 3eltr3d.2 . 2 (𝜑𝐴 = 𝐶)
2 3eltr3d.1 . . 3 (𝜑𝐴𝐵)
3 3eltr3d.3 . . 3 (𝜑𝐵 = 𝐷)
42, 3eleqtrd 2116 . 2 (𝜑𝐴𝐷)
51, 4eqeltrrd 2115 1 (𝜑𝐶𝐷)
Colors of variables: wff set class
Syntax hints:  wi 4   = wceq 1243  wcel 1393
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1336  ax-gen 1338  ax-ie1 1382  ax-ie2 1383  ax-4 1400  ax-17 1419  ax-ial 1427  ax-ext 2022
This theorem depends on definitions:  df-bi 110  df-cleq 2033  df-clel 2036
This theorem is referenced by:  nnaordi  6068  icoshftf1o  8826  lincmb01cmp  8838  fzosubel  9017
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