Metamath Proof Explorer


Theorem btwnswapid2

Description: If you can swap arguments one and three of a betweenness statement, then those arguments are identical. (Contributed by Scott Fenton, 7-Oct-2013)

Ref Expression
Assertion btwnswapid2 ( ( 𝑁 ∈ ℕ ∧ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( ( 𝐴 Btwn ⟨ 𝐵 , 𝐶 ⟩ ∧ 𝐶 Btwn ⟨ 𝐵 , 𝐴 ⟩ ) → 𝐴 = 𝐶 ) )

Proof

Step Hyp Ref Expression
1 btwncom ( ( 𝑁 ∈ ℕ ∧ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( 𝐴 Btwn ⟨ 𝐵 , 𝐶 ⟩ ↔ 𝐴 Btwn ⟨ 𝐶 , 𝐵 ⟩ ) )
2 3anrev ( ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ↔ ( 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ) )
3 btwncom ( ( 𝑁 ∈ ℕ ∧ ( 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( 𝐶 Btwn ⟨ 𝐵 , 𝐴 ⟩ ↔ 𝐶 Btwn ⟨ 𝐴 , 𝐵 ⟩ ) )
4 2 3 sylan2b ( ( 𝑁 ∈ ℕ ∧ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( 𝐶 Btwn ⟨ 𝐵 , 𝐴 ⟩ ↔ 𝐶 Btwn ⟨ 𝐴 , 𝐵 ⟩ ) )
5 1 4 anbi12d ( ( 𝑁 ∈ ℕ ∧ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( ( 𝐴 Btwn ⟨ 𝐵 , 𝐶 ⟩ ∧ 𝐶 Btwn ⟨ 𝐵 , 𝐴 ⟩ ) ↔ ( 𝐴 Btwn ⟨ 𝐶 , 𝐵 ⟩ ∧ 𝐶 Btwn ⟨ 𝐴 , 𝐵 ⟩ ) ) )
6 3ancomb ( ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ↔ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ) )
7 btwnswapid ( ( 𝑁 ∈ ℕ ∧ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( ( 𝐴 Btwn ⟨ 𝐶 , 𝐵 ⟩ ∧ 𝐶 Btwn ⟨ 𝐴 , 𝐵 ⟩ ) → 𝐴 = 𝐶 ) )
8 6 7 sylan2b ( ( 𝑁 ∈ ℕ ∧ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( ( 𝐴 Btwn ⟨ 𝐶 , 𝐵 ⟩ ∧ 𝐶 Btwn ⟨ 𝐴 , 𝐵 ⟩ ) → 𝐴 = 𝐶 ) )
9 5 8 sylbid ( ( 𝑁 ∈ ℕ ∧ ( 𝐴 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐵 ∈ ( 𝔼 ‘ 𝑁 ) ∧ 𝐶 ∈ ( 𝔼 ‘ 𝑁 ) ) ) → ( ( 𝐴 Btwn ⟨ 𝐵 , 𝐶 ⟩ ∧ 𝐶 Btwn ⟨ 𝐵 , 𝐴 ⟩ ) → 𝐴 = 𝐶 ) )