Theorem uneq2i

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

	Ref	Expression
Hypothesis	uneq1i.1	$$⊢A=B$$
Assertion	uneq2i	$$⊢C\cup A=C\cup B$$

Proof

Step	Hyp	Ref	Expression
1		uneq1i.1	$$⊢A=B$$
2		uneq2	$$⊢A=B\to C\cup A=C\cup B$$
3	1 2	ax-mp	$$⊢C\cup A=C\cup B$$