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Theorem notnot1 559
Description: Adding double negation. Theorem *2.12 of [WhiteheadRussell] p. 101. This one holds intuitionistically, but its converse does not (see notnot2dc 750). (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 2-Mar-2013.)
Assertion
Ref Expression
notnot1

Proof of Theorem notnot1
StepHypRef Expression
1 id 19 . 2
21con2i 557 1
Colors of variables: wff set class
Syntax hints:   wn 3   wi 4
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-in1 544  ax-in2 545
This theorem is referenced by:  con3d  560  notnoti  573  pm3.24  626  notnotnot  627  biortn  663  dcn  745  con1dc  752  notnotdc  765  eueq2dc  2708  difsnpssim  3498  xrlttri3  8448  nltpnft  8460  ngtmnft  8461  bdnthALT  9224
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