Theorem eleq1a 2249

Description: A transitive-type law relating membership and equality. (Contributed by NM, 9-Apr-1994.)

Assertion

Ref	Expression
eleq1a	|- ( A e. B -> ( C = A -> C e. B ) )

Proof of Theorem eleq1a

Step	Hyp	Ref	Expression
1		eleq1 2240	. 2 |- ( C = A -> ( C e. B <-> A e. B ) )
2	1	biimprcd 160	1 |- ( A e. B -> ( C = A -> C e. B ) )

Syntax hints:   -> wi 4   = wceq 1353   e. wcel 2148

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 1447  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-4 1510  ax-17 1526  ax-ial 1534  ax-ext 2159

This theorem depends on definitions:  df-bi 117  df-cleq 2170  df-clel 2173

This theorem is referenced by:  elex22  2752  elex2  2753  reu6  2926  disjne  3476  ssimaex  5577  fnex  5738  f1ocnv2d  6074  mpoexw  6213  tfrlem8  6318  eroprf  6627  ac6sfi  6897  recclnq  7390  prnmaddl  7488  renegcl  8217  nn0ind-raph  9369  iccid  9924  4sqlem1  12385  4sqlem4  12389  opnneiid  13600  metrest  13942  coseq0negpitopi  14193  bj-nn0suc  14652  bj-inf2vnlem2  14659  bj-nn0sucALT  14666