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Theorem bj-nndcALT 14446
Description: Alternate proof of nndc 851. (Proof modification is discouraged.) (New usage is discouraged.) (Contributed by BJ, 9-Oct-2019.)
Assertion
Ref Expression
bj-nndcALT  |-  -.  -. DECID  ph

Proof of Theorem bj-nndcALT
StepHypRef Expression
1 notnot 629 . . 3  |-  ( -. 
ph  ->  -.  -.  -.  ph )
2 bj-nnor 14422 . . 3  |-  ( -. 
-.  ( ph  \/  -.  ph )  <->  ( -.  ph 
->  -.  -.  -.  ph ) )
31, 2mpbir 146 . 2  |-  -.  -.  ( ph  \/  -.  ph )
4 df-dc 835 . . 3  |-  (DECID  ph  <->  ( ph  \/  -.  ph ) )
54notbii 668 . 2  |-  ( -. DECID  ph  <->  -.  ( ph  \/  -.  ph ) )
63, 5mtbir 671 1  |-  -.  -. DECID  ph
Colors of variables: wff set class
Syntax hints:   -. wn 3    -> wi 4    \/ wo 708  DECID wdc 834
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 614  ax-in2 615  ax-io 709
This theorem depends on definitions:  df-bi 117  df-dc 835
This theorem is referenced by: (None)
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