Theorem uneq2d

Description: Deduction adding union to the left in a class equality. (Contributed by NM, 29-Mar-1998)

	Ref	Expression
Hypothesis	uneq1d.1	|- ( ph -> A = B )
Assertion	uneq2d	|- ( ph -> ( C u. A ) = ( C u. B ) )

Proof

Step	Hyp	Ref	Expression
1		uneq1d.1	|- ( ph -> A = B )
2		uneq2	|- ( A = B -> ( C u. A ) = ( C u. B ) )
3	1 2	syl	|- ( ph -> ( C u. A ) = ( C u. B ) )