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Theorem iatbtatnnb 27880
Description: Given a implies b, there exists a proof for a implies not not b. (Contributed by Jarvin Udandy, 2-Sep-2016.)
Hypothesis
Ref Expression
iatbtatnnb.1  |-  ( ph  ->  ps )
Assertion
Ref Expression
iatbtatnnb  |-  ( ph  ->  -.  -.  ps )

Proof of Theorem iatbtatnnb
StepHypRef Expression
1 iatbtatnnb.1 . 2  |-  ( ph  ->  ps )
2 notnot 282 . 2  |-  ( ps  <->  -. 
-.  ps )
31, 2sylib 188 1  |-  ( ph  ->  -.  -.  ps )
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-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 177
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