Theorem cvnbtwn

Description: The covers relation implies no in-betweenness. (Contributed by NM, 12-Jun-2004) (New usage is discouraged.)

	Ref	Expression
Assertion	cvnbtwn	⊢ ( ( 𝐴 ∈ Cℋ ∧ 𝐵 ∈ Cℋ ∧ 𝐶 ∈ Cℋ ) → ( 𝐴 ⋖ℋ 𝐵 → ¬ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) )

Proof

Step	Hyp	Ref	Expression
1		cvbr	⊢ ( ( 𝐴 ∈ Cℋ ∧ 𝐵 ∈ Cℋ ) → ( 𝐴 ⋖ℋ 𝐵 ↔ ( 𝐴 ⊊ 𝐵 ∧ ¬ ∃ 𝑥 ∈ Cℋ ( 𝐴 ⊊ 𝑥 ∧ 𝑥 ⊊ 𝐵 ) ) ) )
2		psseq2	⊢ ( 𝑥 = 𝐶 → ( 𝐴 ⊊ 𝑥 ↔ 𝐴 ⊊ 𝐶 ) )
3		psseq1	⊢ ( 𝑥 = 𝐶 → ( 𝑥 ⊊ 𝐵 ↔ 𝐶 ⊊ 𝐵 ) )
4	2 3	anbi12d	⊢ ( 𝑥 = 𝐶 → ( ( 𝐴 ⊊ 𝑥 ∧ 𝑥 ⊊ 𝐵 ) ↔ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) )
5	4	rspcev	⊢ ( ( 𝐶 ∈ Cℋ ∧ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) → ∃ 𝑥 ∈ Cℋ ( 𝐴 ⊊ 𝑥 ∧ 𝑥 ⊊ 𝐵 ) )
6	5	ex	⊢ ( 𝐶 ∈ Cℋ → ( ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) → ∃ 𝑥 ∈ Cℋ ( 𝐴 ⊊ 𝑥 ∧ 𝑥 ⊊ 𝐵 ) ) )
7	6	con3rr3	⊢ ( ¬ ∃ 𝑥 ∈ Cℋ ( 𝐴 ⊊ 𝑥 ∧ 𝑥 ⊊ 𝐵 ) → ( 𝐶 ∈ Cℋ → ¬ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) )
8	7	adantl	⊢ ( ( 𝐴 ⊊ 𝐵 ∧ ¬ ∃ 𝑥 ∈ Cℋ ( 𝐴 ⊊ 𝑥 ∧ 𝑥 ⊊ 𝐵 ) ) → ( 𝐶 ∈ Cℋ → ¬ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) )
9	1 8	syl6bi	⊢ ( ( 𝐴 ∈ Cℋ ∧ 𝐵 ∈ Cℋ ) → ( 𝐴 ⋖ℋ 𝐵 → ( 𝐶 ∈ Cℋ → ¬ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) ) )
10	9	com23	⊢ ( ( 𝐴 ∈ Cℋ ∧ 𝐵 ∈ Cℋ ) → ( 𝐶 ∈ Cℋ → ( 𝐴 ⋖ℋ 𝐵 → ¬ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) ) )
11	10	3impia	⊢ ( ( 𝐴 ∈ Cℋ ∧ 𝐵 ∈ Cℋ ∧ 𝐶 ∈ Cℋ ) → ( 𝐴 ⋖ℋ 𝐵 → ¬ ( 𝐴 ⊊ 𝐶 ∧ 𝐶 ⊊ 𝐵 ) ) )