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Theorem 3eltr3d 2222
 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 2218 . 2 (𝜑𝐴𝐷)
51, 4eqeltrrd 2217 1 (𝜑𝐶𝐷)
 Colors of variables: wff set class Syntax hints:   → wi 4   = wceq 1331   ∈ wcel 1480 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-5 1423  ax-gen 1425  ax-ie1 1469  ax-ie2 1470  ax-4 1487  ax-17 1506  ax-ial 1514  ax-ext 2121 This theorem depends on definitions:  df-bi 116  df-cleq 2132  df-clel 2135 This theorem is referenced by:  reg3exmidlemwe  4493  nnaordi  6404  icoshftf1o  9781  lincmb01cmp  9793  fzosubel  9978  cnmpt2res  12475  dvcnp2cntop  12841
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