Theorem anbi1

Description: Introduce a right conjunct to both sides of a logical equivalence. Theorem *4.36 of WhiteheadRussell p. 118. (Contributed by NM, 3-Jan-2005)

	Ref	Expression
Assertion	anbi1	|- ( ( ph <-> ps ) -> ( ( ph /\ ch ) <-> ( ps /\ ch ) ) )

Proof

Step	Hyp	Ref	Expression
1		id	|- ( ( ph <-> ps ) -> ( ph <-> ps ) )
2	1	anbi1d	|- ( ( ph <-> ps ) -> ( ( ph /\ ch ) <-> ( ps /\ ch ) ) )