Theorem orel2 734

Description: Elimination of disjunction by denial of a disjunct. Theorem *2.56 of [WhiteheadRussell] p. 107. (Contributed by NM, 12-Aug-1994.) (Proof shortened by Wolf Lammen, 5-Apr-2013.)

Assertion

Ref	Expression
orel2	|- ( -. ph -> ( ( ps \/ ph ) -> ps ) )

Proof of Theorem orel2

Step	Hyp	Ref	Expression
1		idd 21	. 2 |- ( -. ph -> ( ps -> ps ) )
2		pm2.21 622	. 2 |- ( -. ph -> ( ph -> ps ) )
3	1, 2	jaod 725	1 |- ( -. ph -> ( ( ps \/ ph ) -> ps ) )

Syntax hints:   -. wn 3   -> wi 4   \/ wo 716

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-in2 620  ax-io 717

This theorem depends on definitions:  df-bi 117

This theorem is referenced by:  biorfi  754  pm2.64  809  stdcn  855  pm5.71dc  970  ecased  1386  19.30dc  1676  dveeq2  1863  prel12  3859  funun  5378  fnpr2ob  13486