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Theorem pm5.21nd 869
Description: Eliminate an antecedent implied by each side of a biconditional. (Contributed by NM, 20-Nov-2005.) (Proof shortened by Wolf Lammen, 4-Nov-2013.)
Hypotheses
Ref Expression
pm5.21nd.1  |-  ( (
ph  /\  ps )  ->  th )
pm5.21nd.2  |-  ( (
ph  /\  ch )  ->  th )
pm5.21nd.3  |-  ( th 
->  ( ps  <->  ch )
)
Assertion
Ref Expression
pm5.21nd  |-  ( ph  ->  ( ps  <->  ch )
)

Proof of Theorem pm5.21nd
StepHypRef Expression
1 pm5.21nd.1 . . 3  |-  ( (
ph  /\  ps )  ->  th )
21ex 424 . 2  |-  ( ph  ->  ( ps  ->  th )
)
3 pm5.21nd.2 . . 3  |-  ( (
ph  /\  ch )  ->  th )
43ex 424 . 2  |-  ( ph  ->  ( ch  ->  th )
)
5 pm5.21nd.3 . . 3  |-  ( th 
->  ( ps  <->  ch )
)
65a1i 11 . 2  |-  ( ph  ->  ( th  ->  ( ps 
<->  ch ) ) )
72, 4, 6pm5.21ndd 344 1  |-  ( ph  ->  ( ps  <->  ch )
)
Colors of variables: wff set class
Syntax hints:    -> wi 4    <-> wb 177    /\ wa 359
This theorem is referenced by:  ordsucelsuc  4794  ideqg  5016  fvelimab  5774  releldm2  6389  relbrtpos  6482  brrpssg  6516  relelec  6937  elfiun  7427  fpwwe2lem2  8499  fpwwelem  8512  fzrev3  11103  elfzp12  11118  eqgval  14981  eltg  17014  eltg2  17015  cncnp2  17337  isdivrngo  22011  isfne  26339  isref  26350  islocfin  26367  opelopab3  26409  islshpkrN  29855  dihatexv2  32074
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 178  df-an 361
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