Theorem uneq1i

Description: Inference adding union to the right in a class equality. (Contributed by NM, 30-Aug-1993)

	Ref	Expression
Hypothesis	uneq1i.1	|- A = B
Assertion	uneq1i	|- ( A u. C ) = ( B u. C )

Proof

Step	Hyp	Ref	Expression
1		uneq1i.1	|- A = B
2		uneq1	|- ( A = B -> ( A u. C ) = ( B u. C ) )
3	1 2	ax-mp	|- ( A u. C ) = ( B u. C )