Theorem padd12N

Description: Commutative/associative law for projective subspace sum. (Contributed by NM, 14-Jan-2012) (New usage is discouraged.)

	Ref	Expression
Hypotheses	paddass.a	⊢ 𝐴 = ( Atoms ‘ 𝐾 )
	paddass.p	⊢ + = ( +𝑃 ‘ 𝐾 )
Assertion	padd12N	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → ( 𝑋 + ( 𝑌 + 𝑍 ) ) = ( 𝑌 + ( 𝑋 + 𝑍 ) ) )

Proof

Step	Hyp	Ref	Expression
1		paddass.a	⊢ 𝐴 = ( Atoms ‘ 𝐾 )
2		paddass.p	⊢ + = ( +𝑃 ‘ 𝐾 )
3		hllat	⊢ ( 𝐾 ∈ HL → 𝐾 ∈ Lat )
4	3	adantr	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → 𝐾 ∈ Lat )
5		simpr1	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → 𝑋 ⊆ 𝐴 )
6		simpr2	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → 𝑌 ⊆ 𝐴 )
7	1 2	paddcom	⊢ ( ( 𝐾 ∈ Lat ∧ 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ) → ( 𝑋 + 𝑌 ) = ( 𝑌 + 𝑋 ) )
8	4 5 6 7	syl3anc	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → ( 𝑋 + 𝑌 ) = ( 𝑌 + 𝑋 ) )
9	8	oveq1d	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → ( ( 𝑋 + 𝑌 ) + 𝑍 ) = ( ( 𝑌 + 𝑋 ) + 𝑍 ) )
10	1 2	paddass	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → ( ( 𝑋 + 𝑌 ) + 𝑍 ) = ( 𝑋 + ( 𝑌 + 𝑍 ) ) )
11		simpl	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → 𝐾 ∈ HL )
12		simpr3	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → 𝑍 ⊆ 𝐴 )
13	1 2	paddass	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑌 ⊆ 𝐴 ∧ 𝑋 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → ( ( 𝑌 + 𝑋 ) + 𝑍 ) = ( 𝑌 + ( 𝑋 + 𝑍 ) ) )
14	11 6 5 12 13	syl13anc	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → ( ( 𝑌 + 𝑋 ) + 𝑍 ) = ( 𝑌 + ( 𝑋 + 𝑍 ) ) )
15	9 10 14	3eqtr3d	⊢ ( ( 𝐾 ∈ HL ∧ ( 𝑋 ⊆ 𝐴 ∧ 𝑌 ⊆ 𝐴 ∧ 𝑍 ⊆ 𝐴 ) ) → ( 𝑋 + ( 𝑌 + 𝑍 ) ) = ( 𝑌 + ( 𝑋 + 𝑍 ) ) )