Theorem nanbi2i

Description: Introduce a left anti-conjunct to both sides of a logical equivalence. (Contributed by SF, 2-Jan-2018)

	Ref	Expression
Hypothesis	nanbii.1	|- ( ph <-> ps )
Assertion	nanbi2i	|- ( ( ch -/\ ph ) <-> ( ch -/\ ps ) )

Proof

Step	Hyp	Ref	Expression
1		nanbii.1	|- ( ph <-> ps )
2		nanbi2	|- ( ( ph <-> ps ) -> ( ( ch -/\ ph ) <-> ( ch -/\ ps ) ) )
3	1 2	ax-mp	|- ( ( ch -/\ ph ) <-> ( ch -/\ ps ) )