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Theorem necon4bid 2664
Description: Contrapositive law deduction for inequality. (Contributed by NM, 29-Jun-2007.)
Hypothesis
Ref Expression
necon4bid.1  |-  ( ph  ->  ( A  =/=  B  <->  C  =/=  D ) )
Assertion
Ref Expression
necon4bid  |-  ( ph  ->  ( A  =  B  <-> 
C  =  D ) )

Proof of Theorem necon4bid
StepHypRef Expression
1 necon4bid.1 . . 3  |-  ( ph  ->  ( A  =/=  B  <->  C  =/=  D ) )
21necon2bbid 2656 . 2  |-  ( ph  ->  ( C  =  D  <->  -.  A  =/=  B
) )
3 nne 2602 . 2  |-  ( -.  A  =/=  B  <->  A  =  B )
42, 3syl6rbb 254 1  |-  ( ph  ->  ( A  =  B  <-> 
C  =  D ) )
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    <-> wb 177    = wceq 1652    =/= wne 2598
This theorem is referenced by:  nebi  2669  znnenlem  12803  rpexp  13112  norm-i  22623  trlid0b  30912
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-ne 2600
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