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Theorem pm5.1im 238
Description: Two propositions are equivalent if they are both true. Closed form of 2th 239. Equivalent to a bi1 186-like version of the xor-connective. This theorem stays true, no matter how you permute its operands. This is evident from its sharper version . (Contributed by Wolf Lammen, 12-May-2013.)
Ref Expression

Proof of Theorem pm5.1im
StepHypRef Expression
1 ax-1 6 . 2
2 ax-1 6 . 2
31, 2impbid21d 190 1
Colors of variables: wff setvar class
Syntax hints:  ->wi 4  <->wb 184
This theorem is referenced by:  2thd  240  pm5.501  341
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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