Theorem oppne1

Description: Points lying on opposite sides of a line cannot be on the line. (Contributed by Thierry Arnoux, 3-Mar-2020)

	Ref	Expression
Hypotheses	hpg.p	⊢ 𝑃 = ( Base ‘ 𝐺 )
	hpg.d	⊢ − = ( dist ‘ 𝐺 )
	hpg.i	⊢ 𝐼 = ( Itv ‘ 𝐺 )
	hpg.o	⊢ 𝑂 = { ⟨ 𝑎 , 𝑏 ⟩ ∣ ( ( 𝑎 ∈ ( 𝑃 ∖ 𝐷 ) ∧ 𝑏 ∈ ( 𝑃 ∖ 𝐷 ) ) ∧ ∃ 𝑡 ∈ 𝐷 𝑡 ∈ ( 𝑎 𝐼 𝑏 ) ) }
	opphl.l	⊢ 𝐿 = ( LineG ‘ 𝐺 )
	opphl.d	⊢ ( 𝜑 → 𝐷 ∈ ran 𝐿 )
	opphl.g	⊢ ( 𝜑 → 𝐺 ∈ TarskiG )
	oppcom.a	⊢ ( 𝜑 → 𝐴 ∈ 𝑃 )
	oppcom.b	⊢ ( 𝜑 → 𝐵 ∈ 𝑃 )
	oppcom.o	⊢ ( 𝜑 → 𝐴 𝑂 𝐵 )
Assertion	oppne1	⊢ ( 𝜑 → ¬ 𝐴 ∈ 𝐷 )

Proof

Step	Hyp	Ref	Expression
1		hpg.p	⊢ 𝑃 = ( Base ‘ 𝐺 )
2		hpg.d	⊢ − = ( dist ‘ 𝐺 )
3		hpg.i	⊢ 𝐼 = ( Itv ‘ 𝐺 )
4		hpg.o	⊢ 𝑂 = { ⟨ 𝑎 , 𝑏 ⟩ ∣ ( ( 𝑎 ∈ ( 𝑃 ∖ 𝐷 ) ∧ 𝑏 ∈ ( 𝑃 ∖ 𝐷 ) ) ∧ ∃ 𝑡 ∈ 𝐷 𝑡 ∈ ( 𝑎 𝐼 𝑏 ) ) }
5		opphl.l	⊢ 𝐿 = ( LineG ‘ 𝐺 )
6		opphl.d	⊢ ( 𝜑 → 𝐷 ∈ ran 𝐿 )
7		opphl.g	⊢ ( 𝜑 → 𝐺 ∈ TarskiG )
8		oppcom.a	⊢ ( 𝜑 → 𝐴 ∈ 𝑃 )
9		oppcom.b	⊢ ( 𝜑 → 𝐵 ∈ 𝑃 )
10		oppcom.o	⊢ ( 𝜑 → 𝐴 𝑂 𝐵 )
11	1 2 3 4 8 9	islnopp	⊢ ( 𝜑 → ( 𝐴 𝑂 𝐵 ↔ ( ( ¬ 𝐴 ∈ 𝐷 ∧ ¬ 𝐵 ∈ 𝐷 ) ∧ ∃ 𝑡 ∈ 𝐷 𝑡 ∈ ( 𝐴 𝐼 𝐵 ) ) ) )
12	10 11	mpbid	⊢ ( 𝜑 → ( ( ¬ 𝐴 ∈ 𝐷 ∧ ¬ 𝐵 ∈ 𝐷 ) ∧ ∃ 𝑡 ∈ 𝐷 𝑡 ∈ ( 𝐴 𝐼 𝐵 ) ) )
13	12	simplld	⊢ ( 𝜑 → ¬ 𝐴 ∈ 𝐷 )