Metamath Proof Explorer

Theorem pm5.5

Description: Theorem *5.5 of WhiteheadRussell p. 125. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm5.5 
|- ( ph -> ( ( ph -> ps ) <-> ps ) )

Proof

Step Hyp Ref Expression
1 biimt 
 |-  ( ph -> ( ps <-> ( ph -> ps ) ) )
2 1 bicomd 
 |-  ( ph -> ( ( ph -> ps ) <-> ps ) )