Theorem hlcomd

Description: The half-line relation is symmetric. Theorem 6.6 of Schwabhauser p. 44. (Contributed by Thierry Arnoux, 21-Feb-2020)

	Ref	Expression
Hypotheses	ishlg.p	⊢ 𝑃 = ( Base ‘ 𝐺 )
	ishlg.i	⊢ 𝐼 = ( Itv ‘ 𝐺 )
	ishlg.k	⊢ 𝐾 = ( hlG ‘ 𝐺 )
	ishlg.a	⊢ ( 𝜑 → 𝐴 ∈ 𝑃 )
	ishlg.b	⊢ ( 𝜑 → 𝐵 ∈ 𝑃 )
	ishlg.c	⊢ ( 𝜑 → 𝐶 ∈ 𝑃 )
	ishlg.g	⊢ ( 𝜑 → 𝐺 ∈ 𝑉 )
	hlcomd.1	⊢ ( 𝜑 → 𝐴 ( 𝐾 ‘ 𝐶 ) 𝐵 )
Assertion	hlcomd	⊢ ( 𝜑 → 𝐵 ( 𝐾 ‘ 𝐶 ) 𝐴 )

Proof

Step	Hyp	Ref	Expression
1		ishlg.p	⊢ 𝑃 = ( Base ‘ 𝐺 )
2		ishlg.i	⊢ 𝐼 = ( Itv ‘ 𝐺 )
3		ishlg.k	⊢ 𝐾 = ( hlG ‘ 𝐺 )
4		ishlg.a	⊢ ( 𝜑 → 𝐴 ∈ 𝑃 )
5		ishlg.b	⊢ ( 𝜑 → 𝐵 ∈ 𝑃 )
6		ishlg.c	⊢ ( 𝜑 → 𝐶 ∈ 𝑃 )
7		ishlg.g	⊢ ( 𝜑 → 𝐺 ∈ 𝑉 )
8		hlcomd.1	⊢ ( 𝜑 → 𝐴 ( 𝐾 ‘ 𝐶 ) 𝐵 )
9	1 2 3 4 5 6 7	hlcomb	⊢ ( 𝜑 → ( 𝐴 ( 𝐾 ‘ 𝐶 ) 𝐵 ↔ 𝐵 ( 𝐾 ‘ 𝐶 ) 𝐴 ) )
10	8 9	mpbid	⊢ ( 𝜑 → 𝐵 ( 𝐾 ‘ 𝐶 ) 𝐴 )