Theorem rmobii

Description: Formula-building rule for restricted at-most-one quantifier (inference form). (Contributed by NM, 16-Jun-2017)

	Ref	Expression
Hypothesis	rmobii.1	|- ( ph <-> ps )
Assertion	rmobii	|- ( E* x e. A ph <-> E* x e. A ps )

Proof

Step	Hyp	Ref	Expression
1		rmobii.1	|- ( ph <-> ps )
2	1	a1i	|- ( x e. A -> ( ph <-> ps ) )
3	2	rmobiia	|- ( E* x e. A ph <-> E* x e. A ps )