Theorem pm2.51 101

Description: Theorem *2.51 of [WhiteheadRussell] p. 107.

Assertion

Ref	Expression
pm2.51	|- (-. (ph -> ps) -> (ph -> -. ps))

Proof of Theorem pm2.51

Step	Hyp	Ref	Expression
1		ax-1 4	. . 3 |- (ps -> (ph -> ps))
2	1	con3i 98	. 2 |- (-. (ph -> ps) -> -. ps)
3	2	a1d 12	1 |- (-. (ph -> ps) -> (ph -> -. ps))

Syntax hints:  -. wn 2   -> wi 3

This theorem is referenced by:  pm5.18 658  pm5.12 661

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

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