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Metamath Proof Explorer

Theorem pm2.61d2

Description: Inference eliminating an antecedent. (Contributed by NM, 18-Aug-1993)

Ref Expression
Hypotheses pm2.61d2.1 
|- ( ph -> ( -. ps -> ch ) )
pm2.61d2.2 
|- ( ps -> ch )
Assertion pm2.61d2 
|- ( ph -> ch )

Proof

Step Hyp Ref Expression
1 pm2.61d2.1 
 |-  ( ph -> ( -. ps -> ch ) )
2 pm2.61d2.2 
 |-  ( ps -> ch )
3 2 a1i 
 |-  ( ph -> ( ps -> ch ) )
4 3 1 pm2.61d 
 |-  ( ph -> ch )