Theorem bnj1262

Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)

	Ref	Expression
Hypotheses	bnj1262.1	|- A C_ B
	bnj1262.2	|- ( ph -> C = A )
Assertion	bnj1262	|- ( ph -> C C_ B )

Proof

Step	Hyp	Ref	Expression
1		bnj1262.1	|- A C_ B
2		bnj1262.2	|- ( ph -> C = A )
3	2 1	eqsstrdi	|- ( ph -> C C_ B )