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Theorem biantr 902
Description: A transitive law of equivalence. Compare Theorem *4.22 of [WhiteheadRussell] p. 117. (Contributed by NM, 18-Aug-1993.)
Assertion
Ref Expression
biantr  |-  ( ( ( ph  <->  ps )  /\  ( ch  <->  ps )
)  ->  ( ph  <->  ch ) )

Proof of Theorem biantr
StepHypRef Expression
1 id 21 . . 3  |-  ( ( ch  <->  ps )  ->  ( ch 
<->  ps ) )
21bibi2d 311 . 2  |-  ( ( ch  <->  ps )  ->  (
( ph  <->  ch )  <->  ( ph  <->  ps ) ) )
32biimparc 475 1  |-  ( ( ( ph  <->  ps )  /\  ( ch  <->  ps )
)  ->  ( ph  <->  ch ) )
Colors of variables: wff set class
Syntax hints:    -> wi 6    <-> wb 178    /\ wa 360
This theorem is referenced by:  bm1.1  2238  bitr3VD  27412  sbcoreleleqVD  27422  trsbcVD  27440  sbcssVD  27446
This theorem was proved from axioms:  ax-1 7  ax-2 8  ax-3 9  ax-mp 10
This theorem depends on definitions:  df-bi 179  df-an 362
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