Theorem orcs

Description: Deduction eliminating disjunct.Notational convention: We sometimes suffix with "s" the label of an inference that manipulates an antecedent, leaving the consequent unchanged. The "s" means that the inference eliminates the need for a syllogism ( syl ) -type inference in a proof. (Contributed by NM, 21-Jun-1994)

	Ref	Expression
Hypothesis	orcs.1	|- ( ( ph \/ ps ) -> ch )
Assertion	orcs	|- ( ph -> ch )

Proof

Step	Hyp	Ref	Expression
1		orcs.1	|- ( ( ph \/ ps ) -> ch )
2		orc	|- ( ph -> ( ph \/ ps ) )
3	2 1	syl	|- ( ph -> ch )