Theorem 3eltr3d 2321

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

Hypotheses

Ref	Expression
3eltr3d.1	|- ( ph -> A e. B )
3eltr3d.2	|- ( ph -> A = C )
3eltr3d.3	|- ( ph -> B = D )

Assertion

Ref	Expression
3eltr3d	|- ( ph -> C e. D )

Proof of Theorem 3eltr3d

Step	Hyp	Ref	Expression
1		3eltr3d.2	. 2 |- ( ph -> A = C )
2		3eltr3d.1	. . 3 |- ( ph -> A e. B )
3		3eltr3d.3	. . 3 |- ( ph -> B = D )
4	2, 3	eleqtrd 2317	. 2 |- ( ph -> A e. D )
5	1, 4	eqeltrrd 2316	1 |- ( ph -> C e. D )

Syntax hints:   -> wi 4   = wceq 1402   e. wcel 2209

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1500  ax-gen 1502  ax-ie1 1546  ax-ie2 1547  ax-4 1563  ax-17 1579  ax-ial 1587  ax-ext 2220

This theorem depends on definitions:  df-bi 117  df-cleq 2231  df-clel 2234

This theorem is referenced by:  reg3exmidlemwe  4721  nnaordi  6771  icoshftf1o  10372  lincmb01cmp  10384  fzosubel  10590  cnmpt2res  15321  dvcnp2cntop  15723