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Theorem 3eqtr2ri 2109
Description: An inference from three chained equalities. (Contributed by NM, 3-Aug-2006.) (Proof shortened by Andrew Salmon, 25-May-2011.)
Hypotheses
Ref Expression
3eqtr2i.1  |-  A  =  B
3eqtr2i.2  |-  C  =  B
3eqtr2i.3  |-  C  =  D
Assertion
Ref Expression
3eqtr2ri  |-  D  =  A

Proof of Theorem 3eqtr2ri
StepHypRef Expression
1 3eqtr2i.1 . . 3  |-  A  =  B
2 3eqtr2i.2 . . 3  |-  C  =  B
31, 2eqtr4i 2105 . 2  |-  A  =  C
4 3eqtr2i.3 . 2  |-  C  =  D
53, 4eqtr2i 2103 1  |-  D  =  A
Colors of variables: wff set class
Syntax hints:    = wceq 1285
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1377  ax-gen 1379  ax-4 1441  ax-17 1460  ax-ext 2064
This theorem depends on definitions:  df-bi 115  df-cleq 2075
This theorem is referenced by:  funimacnv  5006  uniqs  6230
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