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Theorem pm5.21im 349
Description: Two propositions are equivalent if they are both false. Closed form of 2false 350. Equivalent to a bi2 198-like version of the xor-connective. (Contributed by Wolf Lammen, 13-May-2013.)
Ref Expression

Proof of Theorem pm5.21im
StepHypRef Expression
1 nbn2 345 . 2
21biimpd 207 1
Colors of variables: wff setvar class
Syntax hints:  -.wn 3  ->wi 4  <->wb 184
This theorem is referenced by:  pm5.21ndd  354  pm5.21  858
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 185
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