Theorem pm5.41 249

Description: Theorem *5.41 of [WhiteheadRussell] p. 125. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 12-Oct-2012.)

Assertion

Ref	Expression
pm5.41	|- ( ( ( ph -> ps ) -> ( ph -> ch ) ) <-> ( ph -> ( ps -> ch ) ) )

Proof of Theorem pm5.41

Step	Hyp	Ref	Expression
1		imdi 248	. 2 |- ( ( ph -> ( ps -> ch ) ) <-> ( ( ph -> ps ) -> ( ph -> ch ) ) )
2	1	bicomi 130	1 |- ( ( ( ph -> ps ) -> ( ph -> ch ) ) <-> ( ph -> ( ps -> ch ) ) )

Syntax hints:   -> wi 4   <-> wb 103

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106

This theorem depends on definitions:  df-bi 115

This theorem is referenced by: (None)