Metamath Proof Explorer

Theorem pm2.64

Description: Theorem *2.64 of WhiteheadRussell p. 107. (Contributed by NM, 3-Jan-2005)

Ref Expression
Assertion pm2.64 
|- ( ( ph \/ ps ) -> ( ( ph \/ -. ps ) -> ph ) )

Proof

Step Hyp Ref Expression
1 orel2 
 |-  ( -. ps -> ( ( ph \/ ps ) -> ph ) )
2 1 jao1i 
 |-  ( ( ph \/ -. ps ) -> ( ( ph \/ ps ) -> ph ) )
3 2 com12 
 |-  ( ( ph \/ ps ) -> ( ( ph \/ -. ps ) -> ph ) )