Theorem an12i

Description: An inference from commuting operands in a chain of conjunctions. (Contributed by Giovanni Mascellani, 22-May-2019)

	Ref	Expression
Hypothesis	an12i.1	|- ( ph /\ ( ps /\ ch ) )
Assertion	an12i	|- ( ps /\ ( ph /\ ch ) )

Proof

Step	Hyp	Ref	Expression
1		an12i.1	|- ( ph /\ ( ps /\ ch ) )
2		an12	|- ( ( ps /\ ( ph /\ ch ) ) <-> ( ph /\ ( ps /\ ch ) ) )
3	1 2	mpbir	|- ( ps /\ ( ph /\ ch ) )