Theorem notnoti 102

Description: Infer double negation.

Hypothesis

Ref	Expression
negbi.1	|- ph

Assertion

Ref	Expression
notnoti	|- -. -. ph

Proof of Theorem notnoti

Step	Hyp	Ref	Expression
1		negbi.1	. 2 |- ph
2		notnot1 101	. 2 |- (ph -> -. -. ph)
3	1, 2	ax-mp 7	1 |- -. -. ph

Syntax hints:  -. wn 2

This theorem is referenced by:  nbn3 789  0nelelxp 3878  dm0OLD 3982  nextnt 13885  amosym1 13980  heiborlem41 15677

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7

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