Theorem dissym1

Description: A symmetry with \/ .

See negsym1 for more information. (Contributed by Anthony Hart, 4-Sep-2011)

	Ref	Expression
Assertion	dissym1	|- ( ( ps \/ ( ps \/ F. ) ) -> ( ps \/ ph ) )

Proof

Step	Hyp	Ref	Expression
1		orc	|- ( ps -> ( ps \/ ph ) )
2		falim	|- ( F. -> ph )
3	2	orim2i	|- ( ( ps \/ F. ) -> ( ps \/ ph ) )
4	1 3	jaoi	|- ( ( ps \/ ( ps \/ F. ) ) -> ( ps \/ ph ) )