Theorem pm2.21ni 92

Description: Inference related to pm2.21 71.

Hypothesis

Ref	Expression
pm2.21ni.1	|- ph

Assertion

Ref	Expression
pm2.21ni	|- (-. ph -> ps)

Proof of Theorem pm2.21ni

Step	Hyp	Ref	Expression
1		pm2.21ni.1	. . 3 |- ph
2	1	a1i 7	. 2 |- (-. ps -> ph)
3	2	con1i 88	1 |- (-. ph -> ps)

Syntax hints:  -. wn 1   -> wi 2

This theorem is referenced by:  niabn 566  snsspr 1853  nneo 4719

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

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