Theorem bj-snglsstag

Description: The singletonization is included in the tagging. (Contributed by BJ, 6-Oct-2018)

	Ref	Expression
Assertion	bj-snglsstag	$$⊢snglA\subseteq tagA$$

Proof

Step	Hyp	Ref	Expression
1		ssun1	$$⊢snglA\subseteq snglA\cup \left\{\varnothing \right\}$$
2		df-bj-tag	$$⊢tagA=snglA\cup \left\{\varnothing \right\}$$
3	1 2	sseqtrri	$$⊢snglA\subseteq tagA$$