Theorem eqtri

Description: An equality transitivity inference. (Contributed by NM, 26-May-1993)

	Ref	Expression
Hypotheses	eqtri.1	$$⊢A=B$$
	eqtri.2	$$⊢B=C$$
Assertion	eqtri	$$⊢A=C$$

Proof

Step	Hyp	Ref	Expression
1		eqtri.1	$$⊢A=B$$
2		eqtri.2	$$⊢B=C$$
3	2	eqeq2i	$$⊢A=B\leftrightarrow A=C$$
4	1 3	mpbi	$$⊢A=C$$