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Theorem notnoti 584
Description: Infer double negation. (Contributed by NM, 27-Feb-2008.)
Hypothesis
Ref Expression
negbi.1  |-  ph
Assertion
Ref Expression
notnoti  |-  -.  -.  ph

Proof of Theorem notnoti
StepHypRef Expression
1 negbi.1 . 2  |-  ph
2 notnot 569 . 2  |-  ( ph  ->  -.  -.  ph )
31, 2ax-mp 7 1  |-  -.  -.  ph
Colors of variables: wff set class
Syntax hints:   -. wn 3
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-in1 554  ax-in2 555
This theorem is referenced by:  nbn3  626  fal  1266  ax-9  1440  neirr  2229  dfnul2  3253  dfnul3  3254  rab0  3273
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