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Theorem orordi 768
Description: Distribution of disjunction over disjunction. (Contributed by NM, 25-Feb-1995.)
Assertion
Ref Expression
orordi  |-  ( (
ph  \/  ( ps  \/  ch ) )  <->  ( ( ph  \/  ps )  \/  ( ph  \/  ch ) ) )

Proof of Theorem orordi
StepHypRef Expression
1 oridm 752 . . 3  |-  ( (
ph  \/  ph )  <->  ph )
21orbi1i 758 . 2  |-  ( ( ( ph  \/  ph )  \/  ( ps  \/  ch ) )  <->  ( ph  \/  ( ps  \/  ch ) ) )
3 or4 766 . 2  |-  ( ( ( ph  \/  ph )  \/  ( ps  \/  ch ) )  <->  ( ( ph  \/  ps )  \/  ( ph  \/  ch ) ) )
42, 3bitr3i 185 1  |-  ( (
ph  \/  ( ps  \/  ch ) )  <->  ( ( ph  \/  ps )  \/  ( ph  \/  ch ) ) )
Colors of variables: wff set class
Syntax hints:    <-> wb 104    \/ wo 703
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-io 704
This theorem depends on definitions:  df-bi 116
This theorem is referenced by: (None)
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