Theorem bnj251

Description: /\ -manipulation. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)

	Ref	Expression
Assertion	bnj251	|- ( ( ph /\ ps /\ ch /\ th ) <-> ( ph /\ ( ps /\ ( ch /\ th ) ) ) )

Proof

Step	Hyp	Ref	Expression
1		bnj250	|- ( ( ph /\ ps /\ ch /\ th ) <-> ( ph /\ ( ( ps /\ ch ) /\ th ) ) )
2		anass	|- ( ( ( ps /\ ch ) /\ th ) <-> ( ps /\ ( ch /\ th ) ) )
3	2	anbi2i	|- ( ( ph /\ ( ( ps /\ ch ) /\ th ) ) <-> ( ph /\ ( ps /\ ( ch /\ th ) ) ) )
4	1 3	bitri	|- ( ( ph /\ ps /\ ch /\ th ) <-> ( ph /\ ( ps /\ ( ch /\ th ) ) ) )