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Theorem con1b 333
Description: Contraposition. Bidirectional version of con1 128. (Contributed by NM, 3-Jan-1993.)
Assertion
Ref Expression
con1b

Proof of Theorem con1b
StepHypRef Expression
1 con1 128 . 2
2 con1 128 . 2
31, 2impbii 188 1
Colors of variables: wff setvar class
Syntax hints:  -.wn 3  ->wi 4  <->wb 184
This theorem is referenced by:  eximal  1615  r19.23v  2937  pwssun  4791  ist1-2  19848  cmpfi  19908  dchrelbas2  23512
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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