Theorem pm4.43 968

Description: Theorem *4.43 of [WhiteheadRussell] p. 119. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 26-Nov-2012.)

Assertion

Ref	Expression
pm4.43	|- ( ph <-> ( ( ph \/ ps ) /\ ( ph \/ -. ps ) ) )

Proof of Theorem pm4.43

Step	Hyp	Ref	Expression
1		pm3.24 926	. . 3 |- -. ( ps /\ -. ps )
2	1	biorfi 422	. 2 |- ( ph <-> ( ph \/ ( ps /\ -. ps ) ) )
3		ordi 908	. 2 |- ( ( ph \/ ( ps /\ -. ps ) ) <-> ( ( ph \/ ps ) /\ ( ph \/ -. ps ) ) )
4	2, 3	bitri 264	1 |- ( ph <-> ( ( ph \/ ps ) /\ ( ph \/ -. ps ) ) )

Syntax hints:   -. wn 3   <-> wb 196   \/ wo 383   /\ wa 384

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386

This theorem is referenced by:  stoweidlem26  40243