Theorem jcn 641

Description: Theorem joining the consequents of two premises. Theorem 8 of [Margaris] p. 60. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Josh Purinton, 29-Dec-2000.)

Assertion

Ref	Expression
jcn	|- ( ph -> ( -. ps -> -. ( ph -> ps ) ) )

Proof of Theorem jcn

Step	Hyp	Ref	Expression
1		pm2.27 40	. 2 |- ( ph -> ( ( ph -> ps ) -> ps ) )
2	1	con3d 621	1 |- ( ph -> ( -. ps -> -. ( ph -> ps ) ) )

Syntax hints:   -. wn 3   -> wi 4

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-in1 604  ax-in2 605

This theorem is referenced by:  jcnd  642  bj-nnim  13616