Theorem uneq1d

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

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

Proof

Step	Hyp	Ref	Expression
1		uneq1d.1	|- ( ph -> A = B )
2		uneq1	|- ( A = B -> ( A u. C ) = ( B u. C ) )
3	1 2	syl	|- ( ph -> ( A u. C ) = ( B u. C ) )