Metamath Proof Explorer

Theorem con4d

Description: Deduction associated with con4 . (Contributed by NM, 26-Mar-1995)

Ref Expression
Hypothesis con4d.1 
|- ( ph -> ( -. ps -> -. ch ) )
Assertion con4d 
|- ( ph -> ( ch -> ps ) )

Proof

Step Hyp Ref Expression
1 con4d.1 
 |-  ( ph -> ( -. ps -> -. ch ) )
2 con4 
 |-  ( ( -. ps -> -. ch ) -> ( ch -> ps ) )
3 1 2 syl 
 |-  ( ph -> ( ch -> ps ) )