Theorem 3eltr4d 2254

Description: Substitution of equal classes into membership relation. (Contributed by Mario Carneiro, 6-Jan-2017.)

Hypotheses

Ref	Expression
3eltr4d.1	⊢ (𝜑 → 𝐴 ∈ 𝐵)
3eltr4d.2	⊢ (𝜑 → 𝐶 = 𝐴)
3eltr4d.3	⊢ (𝜑 → 𝐷 = 𝐵)

Assertion

Ref	Expression
3eltr4d	⊢ (𝜑 → 𝐶 ∈ 𝐷)

Proof of Theorem 3eltr4d

Step	Hyp	Ref	Expression
1		3eltr4d.2	. 2 ⊢ (𝜑 → 𝐶 = 𝐴)
2		3eltr4d.1	. . 3 ⊢ (𝜑 → 𝐴 ∈ 𝐵)
3		3eltr4d.3	. . 3 ⊢ (𝜑 → 𝐷 = 𝐵)
4	2, 3	eleqtrrd 2250	. 2 ⊢ (𝜑 → 𝐴 ∈ 𝐷)
5	1, 4	eqeltrd 2247	1 ⊢ (𝜑 → 𝐶 ∈ 𝐷)

Syntax hints:   → wi 4   = wceq 1348   ∈ wcel 2141

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 1440  ax-gen 1442  ax-ie1 1486  ax-ie2 1487  ax-4 1503  ax-17 1519  ax-ial 1527  ax-ext 2152

This theorem depends on definitions:  df-bi 116  df-cleq 2163  df-clel 2166

This theorem is referenced by:  ovmpodxf  5978  nnaordi  6487  iccf1o  9961  nnmindc  11989  ennnfonelemrn  12374  ctiunctlemfo  12394  mndpropd  12676