Theorem jarl 648

Description: Elimination of a nested antecedent. (Contributed by Wolf Lammen, 10-May-2013.)

Assertion

Ref	Expression
jarl	|- ( ( ( ph -> ps ) -> ch ) -> ( -. ph -> ch ) )

Proof of Theorem jarl

Step	Hyp	Ref	Expression
1		pm2.21 607	. 2 |- ( -. ph -> ( ph -> ps ) )
2	1	imim1i 60	1 |- ( ( ( ph -> ps ) -> ch ) -> ( -. ph -> ch ) )

Syntax hints:   -. wn 3   -> wi 4

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-in2 605

This theorem is referenced by:  pm2.68dc  884