Theorem chseli

Description: Membership in subspace sum. (Contributed by NM, 19-Oct-1999) (New usage is discouraged.)

	Ref	Expression
Hypotheses	ch0le.1	⊢ 𝐴 ∈ Cℋ
	chjcl.2	⊢ 𝐵 ∈ Cℋ
Assertion	chseli	⊢ ( 𝐶 ∈ ( 𝐴 +ℋ 𝐵 ) ↔ ∃ 𝑥 ∈ 𝐴 ∃ 𝑦 ∈ 𝐵 𝐶 = ( 𝑥 +ℎ 𝑦 ) )

Proof

Step	Hyp	Ref	Expression
1		ch0le.1	⊢ 𝐴 ∈ Cℋ
2		chjcl.2	⊢ 𝐵 ∈ Cℋ
3	1	chshii	⊢ 𝐴 ∈ Sℋ
4	2	chshii	⊢ 𝐵 ∈ Sℋ
5	3 4	shseli	⊢ ( 𝐶 ∈ ( 𝐴 +ℋ 𝐵 ) ↔ ∃ 𝑥 ∈ 𝐴 ∃ 𝑦 ∈ 𝐵 𝐶 = ( 𝑥 +ℎ 𝑦 ) )