Theorem sseqtrri

Description: Substitution of equality into a subclass relationship. (Contributed by NM, 4-Apr-1995)

	Ref	Expression
Hypotheses	sseqtrri.1	$$⊢A\subseteq B$$
	sseqtrri.2	$$⊢C=B$$
Assertion	sseqtrri	$$⊢A\subseteq C$$

Proof

Step	Hyp	Ref	Expression
1		sseqtrri.1	$$⊢A\subseteq B$$
2		sseqtrri.2	$$⊢C=B$$
3	2	eqcomi	$$⊢B=C$$
4	1 3	sseqtri	$$⊢A\subseteq C$$