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Theorem orbi1 686
Description: Theorem *4.37 of [WhiteheadRussell] p. 118. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
orbi1  |-  ( (
ph 
<->  ps )  ->  (
( ph  \/  ch ) 
<->  ( ps  \/  ch ) ) )

Proof of Theorem orbi1
StepHypRef Expression
1 id 19 . 2  |-  ( (
ph 
<->  ps )  ->  ( ph 
<->  ps ) )
21orbi1d 683 1  |-  ( (
ph 
<->  ps )  ->  (
( ph  \/  ch ) 
<->  ( ps  \/  ch ) ) )
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 176    \/ wo 357
This theorem is referenced by:  prmdvdsexp  12809  orbi1rVD  28940  sbc3orgVD  28943
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 177  df-or 359
  Copyright terms: Public domain W3C validator