Theorem pm2.68dc 899

Description: Concluding disjunction from implication for a decidable proposition. Based on theorem *2.68 of [WhiteheadRussell] p. 108. Converse of pm2.62 753 and one half of dfor2dc 900. (Contributed by Jim Kingdon, 27-Mar-2018.)

Assertion

Ref	Expression
pm2.68dc	|- (DECID ph -> ( ( ( ph -> ps ) -> ps ) -> ( ph \/ ps ) ) )

Proof of Theorem pm2.68dc

Step	Hyp	Ref	Expression
1		jarl 662	. 2 |- ( ( ( ph -> ps ) -> ps ) -> ( -. ph -> ps ) )
2		pm2.54dc 896	. 2 |- (DECID ph -> ( ( -. ph -> ps ) -> ( ph \/ ps ) ) )
3	1, 2	syl5 32	1 |- (DECID ph -> ( ( ( ph -> ps ) -> ps ) -> ( ph \/ ps ) ) )

Syntax hints:   -. wn 3   -> wi 4   \/ wo 713  DECID wdc 839

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 617  ax-in2 618  ax-io 714

This theorem depends on definitions:  df-bi 117  df-dc 840

This theorem is referenced by:  dfor2dc  900