Theorem shsub1i

Description: Subspace sum is an upper bound of its arguments. (Contributed by NM, 19-Oct-1999) (New usage is discouraged.)

	Ref	Expression
Hypotheses	shincl.1	|- A e. SH
	shincl.2	|- B e. SH
Assertion	shsub1i	|- A C_ ( A +H B )

Proof

Step	Hyp	Ref	Expression
1		shincl.1	|- A e. SH
2		shincl.2	|- B e. SH
3	1 2	shsel1i	|- ( x e. A -> x e. ( A +H B ) )
4	3	ssriv	|- A C_ ( A +H B )