Theorem orel2 213

Description: Elimination of disjunction by denial of a disjunct. Theorem *2.56 of [WhiteheadRussell] p. 107.

Assertion

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

Proof of Theorem orel2

Step	Hyp	Ref	Expression
1		orel1 212	. 2 |- (-. ph -> ((ph \/ ps) -> ps))
2		orcom 209	. 2 |- ((ps \/ ph) <-> (ph \/ ps))
3	1, 2	syl5ib 181	1 |- (-. ph -> ((ps \/ ph) -> ps))

Syntax hints:  -. wn 1   -> wi 2   \/ wo 195

This theorem is referenced by:  prel12 1875  funun 2700

This theorem was proved from axioms:  ax-1 3  ax-2 4  ax-3 5  ax-mp 6

This theorem depends on definitions:  df-bi 128  df-or 197

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