Metamath Proof Explorer

Theorem pm4.24

Description: Theorem *4.24 of WhiteheadRussell p. 117. (Contributed by NM, 11-May-1993)

Ref Expression
Assertion pm4.24 
|- ( ph <-> ( ph /\ ph ) )

Proof

Step Hyp Ref Expression
1 id 
 |-  ( ph -> ph )
2 1 pm4.71i 
 |-  ( ph <-> ( ph /\ ph ) )