Theorem pm2.51 145

Description: Theorem *2.51 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)

Assertion

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

Proof of Theorem pm2.51

Step	Hyp	Ref	Expression
1		ax-1 6	. . 3 |- (ps -> (ph -> ps))
2	1	con3i 127	. 2 |- (-. (ph -> ps) -> -. ps)
3	2	a1d 22	1 |- (-. (ph -> ps) -> (ph -> -. ps))

Syntax hints:  -. wn 3   -> wi 4

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem is referenced by:  pm5.12  855