Theorem orel1 644

Description: Elimination of disjunction by denial of a disjunct. Theorem *2.55 of [WhiteheadRussell] p. 107. (Contributed by NM, 12-Aug-1994.) (Proof shortened by Wolf Lammen, 21-Jul-2012.)

Assertion

Ref	Expression
orel1	|- ( -. ph -> ( ( ph \/ ps ) -> ps ) )

Proof of Theorem orel1

Step	Hyp	Ref	Expression
1		pm2.53 641	. 2 |- ( ( ph \/ ps ) -> ( -. ph -> ps ) )
2	1	com12 27	1 |- ( -. ph -> ( ( ph \/ ps ) -> ps ) )

Syntax hints:   -. wn 3   -> wi 4   \/ wo 629

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-in2 545  ax-io 630

This theorem depends on definitions:  df-bi 110

This theorem is referenced by:  biorf  663  pm2.25dc  792  pm2.85dc  811  euor2  1958  prel12  3542  funun  4944  acexmidlema  5503  acexmidlemb  5504