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Theorem necon3bii 2344
Description: Inference from equality to inequality. (Contributed by NM, 23-Feb-2005.)
Hypothesis
Ref Expression
necon3bii.1  |-  ( A  =  B  <->  C  =  D )
Assertion
Ref Expression
necon3bii  |-  ( A  =/=  B  <->  C  =/=  D )

Proof of Theorem necon3bii
StepHypRef Expression
1 necon3bii.1 . . 3  |-  ( A  =  B  <->  C  =  D )
21necon3abii 2342 . 2  |-  ( A  =/=  B  <->  -.  C  =  D )
3 df-ne 2307 . 2  |-  ( C  =/=  D  <->  -.  C  =  D )
42, 3bitr4i 186 1  |-  ( A  =/=  B  <->  C  =/=  D )
Colors of variables: wff set class
Syntax hints:   -. wn 3    <-> wb 104    = wceq 1331    =/= wne 2306
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-in1 603  ax-in2 604
This theorem depends on definitions:  df-bi 116  df-ne 2307
This theorem is referenced by:  necom  2390  negne0bi  8028
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