Theorem bitr2i

Description: An inference from transitive law for logical equivalence. (Contributed by NM, 12-Mar-1993)

	Ref	Expression
Hypotheses	bitr2i.1	$$⊢\phi \leftrightarrow \psi$$
	bitr2i.2	$$⊢\psi \leftrightarrow \chi$$
Assertion	bitr2i	$$⊢\chi \leftrightarrow \phi$$

Proof

Step	Hyp	Ref	Expression
1		bitr2i.1	$$⊢\phi \leftrightarrow \psi$$
2		bitr2i.2	$$⊢\psi \leftrightarrow \chi$$
3	1 2	bitri	$$⊢\phi \leftrightarrow \chi$$
4	3	bicomi	$$⊢\chi \leftrightarrow \phi$$