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Theorem notnoti 617
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 601 . 2  |-  ( ph  ->  -.  -.  ph )
31, 2ax-mp 5 1  |-  -.  -.  ph
Colors of variables: wff set class
Syntax hints:   -. wn 3
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-in1 586  ax-in2 587
This theorem is referenced by:  nbn3  672  fal  1321  ax-9  1494  neirr  2292  dfnul2  3333  dfnul3  3334  rab0  3359
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