Theorem pm2.521 146

Description: Theorem *2.521 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 8-Oct-2012.)

Assertion

Ref	Expression
pm2.521	|- (-. (ph -> ps) -> (ps -> ph))

Proof of Theorem pm2.521

Step	Hyp	Ref	Expression
1		simplim 143	. 2 |- (-. (ph -> ps) -> ph)
2	1	a1d 22	1 |- (-. (ph -> ps) -> (ps -> ph))

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:  pm2.52  147  loolin  173