Theorem pm2.6dc 862

Description: Case elimination for a decidable proposition. Based on theorem *2.6 of [WhiteheadRussell] p. 107. (Contributed by Jim Kingdon, 25-Mar-2018.)

Assertion

Ref	Expression
pm2.6dc	|- (DECID ph -> ( ( -. ph -> ps ) -> ( ( ph -> ps ) -> ps ) ) )

Proof of Theorem pm2.6dc

Step	Hyp	Ref	Expression
1		pm2.1dc 837	. . 3 |- (DECID ph -> ( -. ph \/ ph ) )
2		pm3.44 715	. . 3 |- ( ( ( -. ph -> ps ) /\ ( ph -> ps ) ) -> ( ( -. ph \/ ph ) -> ps ) )
3	1, 2	syl5com 29	. 2 |- (DECID ph -> ( ( ( -. ph -> ps ) /\ ( ph -> ps ) ) -> ps ) )
4	3	expd 258	1 |- (DECID ph -> ( ( -. ph -> ps ) -> ( ( ph -> ps ) -> ps ) ) )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 104   \/ wo 708  DECID wdc 834

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-io 709

This theorem depends on definitions:  df-bi 117  df-dc 835

This theorem is referenced by:  jadc  863  jaddc  864  pm2.61dc  865