Theorem ex-natded5.7-2

Description: A more efficient proof of Theorem 5.7 of Clemente p. 19. Compare with ex-natded5.7 . (Contributed by Mario Carneiro, 9-Feb-2017) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Hypothesis	ex-natded5.7.1	|- ( ph -> ( ps \/ ( ch /\ th ) ) )
Assertion	ex-natded5.7-2	|- ( ph -> ( ps \/ ch ) )

Proof

Step	Hyp	Ref	Expression
1		ex-natded5.7.1	|- ( ph -> ( ps \/ ( ch /\ th ) ) )
2		simpl	|- ( ( ch /\ th ) -> ch )
3	2	orim2i	|- ( ( ps \/ ( ch /\ th ) ) -> ( ps \/ ch ) )
4	1 3	syl	|- ( ph -> ( ps \/ ch ) )