Theorem eqtrdi

Description: An equality transitivity deduction. (Contributed by NM, 21-Jun-1993)

	Ref	Expression
Hypotheses	eqtrdi.1	|- ( ph -> A = B )
	eqtrdi.2	|- B = C
Assertion	eqtrdi	|- ( ph -> A = C )

Proof

Step	Hyp	Ref	Expression
1		eqtrdi.1	|- ( ph -> A = B )
2		eqtrdi.2	|- B = C
3	2	a1i	|- ( ph -> B = C )
4	1 3	eqtrd	|- ( ph -> A = C )