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Theorem necon4abid 2510
Description: Contrapositive law deduction for inequality. (Contributed by NM, 11-Jan-2008.)
Hypothesis
Ref Expression
necon4abid.1  |-  ( ph  ->  ( A  =/=  B  <->  -. 
ps ) )
Assertion
Ref Expression
necon4abid  |-  ( ph  ->  ( A  =  B  <->  ps ) )

Proof of Theorem necon4abid
StepHypRef Expression
1 df-ne 2448 . . 3  |-  ( A  =/=  B  <->  -.  A  =  B )
2 necon4abid.1 . . 3  |-  ( ph  ->  ( A  =/=  B  <->  -. 
ps ) )
31, 2syl5bbr 250 . 2  |-  ( ph  ->  ( -.  A  =  B  <->  -.  ps )
)
43con4bid 284 1  |-  ( ph  ->  ( A  =  B  <->  ps ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 176    = wceq 1623    =/= wne 2446
This theorem is referenced by:  necon4bbid  2511  birthdaylem3  20248  nmounbi  21354
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-ne 2448
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