Theorem eqtr4di

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

	Ref	Expression
Hypotheses	eqtr4di.1	|- ( ph -> A = B )
	eqtr4di.2	|- C = B
Assertion	eqtr4di	|- ( ph -> A = C )

Proof

Step	Hyp	Ref	Expression
1		eqtr4di.1	|- ( ph -> A = B )
2		eqtr4di.2	|- C = B
3	2	eqcomi	|- B = C
4	1 3	eqtrdi	|- ( ph -> A = C )