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	$$⊢A\cup C=B\cup C$$

Proof

Step	Hyp	Ref	Expression
1		uneq1i.1	$$⊢A=B$$
2		uneq1	$$⊢A=B\to A\cup C=B\cup C$$
3	1 2	ax-mp	$$⊢A\cup C=B\cup C$$