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Theorem nbbn 358
Description: Move negation outside of biconditional. Compare Theorem *5.18 of [WhiteheadRussell] p. 124. (Contributed by NM, 27-Jun-2002.) (Proof shortened by Wolf Lammen, 20-Sep-2013.)
Assertion
Ref Expression
nbbn

Proof of Theorem nbbn
StepHypRef Expression
1 xor3 357 . 2
2 con2bi 328 . 2
3 bicom 200 . 2
41, 2, 33bitrri 272 1
Colors of variables: wff setvar class
Syntax hints:  -.wn 3  <->wb 184
This theorem is referenced by:  biass  359  pclem6  930  xorass  1367  xorneg1  1373  trubifal  1434  hadbi  1454  canth  6254  qextltlem  11430  onint1  29914  notbinot1  30476  notbinot2  30480
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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