Proof of Theorem iccneg
| Step | Hyp | Ref
 | Expression | 
| 1 |   | renegcl 8287 | 
. . . . 5
⊢ (𝐶 ∈ ℝ → -𝐶 ∈
ℝ) | 
| 2 |   | ax-1 6 | 
. . . . 5
⊢ (𝐶 ∈ ℝ → (-𝐶 ∈ ℝ → 𝐶 ∈
ℝ)) | 
| 3 | 1, 2 | impbid2 143 | 
. . . 4
⊢ (𝐶 ∈ ℝ → (𝐶 ∈ ℝ ↔ -𝐶 ∈
ℝ)) | 
| 4 | 3 | 3ad2ant3 1022 | 
. . 3
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐶 ∈ ℝ ↔ -𝐶 ∈
ℝ)) | 
| 5 |   | ancom 266 | 
. . . 4
⊢ ((𝐶 ≤ 𝐵 ∧ 𝐴 ≤ 𝐶) ↔ (𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵)) | 
| 6 |   | leneg 8492 | 
. . . . . . 7
⊢ ((𝐶 ∈ ℝ ∧ 𝐵 ∈ ℝ) → (𝐶 ≤ 𝐵 ↔ -𝐵 ≤ -𝐶)) | 
| 7 | 6 | ancoms 268 | 
. . . . . 6
⊢ ((𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐶 ≤ 𝐵 ↔ -𝐵 ≤ -𝐶)) | 
| 8 | 7 | 3adant1 1017 | 
. . . . 5
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐶 ≤ 𝐵 ↔ -𝐵 ≤ -𝐶)) | 
| 9 |   | leneg 8492 | 
. . . . . 6
⊢ ((𝐴 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐴 ≤ 𝐶 ↔ -𝐶 ≤ -𝐴)) | 
| 10 | 9 | 3adant2 1018 | 
. . . . 5
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐴 ≤ 𝐶 ↔ -𝐶 ≤ -𝐴)) | 
| 11 | 8, 10 | anbi12d 473 | 
. . . 4
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → ((𝐶 ≤ 𝐵 ∧ 𝐴 ≤ 𝐶) ↔ (-𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴))) | 
| 12 | 5, 11 | bitr3id 194 | 
. . 3
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → ((𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵) ↔ (-𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴))) | 
| 13 | 4, 12 | anbi12d 473 | 
. 2
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → ((𝐶 ∈ ℝ ∧ (𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵)) ↔ (-𝐶 ∈ ℝ ∧ (-𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴)))) | 
| 14 |   | elicc2 10013 | 
. . . 4
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → (𝐶 ∈ (𝐴[,]𝐵) ↔ (𝐶 ∈ ℝ ∧ 𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵))) | 
| 15 | 14 | 3adant3 1019 | 
. . 3
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐶 ∈ (𝐴[,]𝐵) ↔ (𝐶 ∈ ℝ ∧ 𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵))) | 
| 16 |   | 3anass 984 | 
. . 3
⊢ ((𝐶 ∈ ℝ ∧ 𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵) ↔ (𝐶 ∈ ℝ ∧ (𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵))) | 
| 17 | 15, 16 | bitrdi 196 | 
. 2
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐶 ∈ (𝐴[,]𝐵) ↔ (𝐶 ∈ ℝ ∧ (𝐴 ≤ 𝐶 ∧ 𝐶 ≤ 𝐵)))) | 
| 18 |   | renegcl 8287 | 
. . . . 5
⊢ (𝐵 ∈ ℝ → -𝐵 ∈
ℝ) | 
| 19 |   | renegcl 8287 | 
. . . . 5
⊢ (𝐴 ∈ ℝ → -𝐴 ∈
ℝ) | 
| 20 |   | elicc2 10013 | 
. . . . 5
⊢ ((-𝐵 ∈ ℝ ∧ -𝐴 ∈ ℝ) → (-𝐶 ∈ (-𝐵[,]-𝐴) ↔ (-𝐶 ∈ ℝ ∧ -𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴))) | 
| 21 | 18, 19, 20 | syl2anr 290 | 
. . . 4
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → (-𝐶 ∈ (-𝐵[,]-𝐴) ↔ (-𝐶 ∈ ℝ ∧ -𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴))) | 
| 22 | 21 | 3adant3 1019 | 
. . 3
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (-𝐶 ∈ (-𝐵[,]-𝐴) ↔ (-𝐶 ∈ ℝ ∧ -𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴))) | 
| 23 |   | 3anass 984 | 
. . 3
⊢ ((-𝐶 ∈ ℝ ∧ -𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴) ↔ (-𝐶 ∈ ℝ ∧ (-𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴))) | 
| 24 | 22, 23 | bitrdi 196 | 
. 2
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (-𝐶 ∈ (-𝐵[,]-𝐴) ↔ (-𝐶 ∈ ℝ ∧ (-𝐵 ≤ -𝐶 ∧ -𝐶 ≤ -𝐴)))) | 
| 25 | 13, 17, 24 | 3bitr4d 220 | 
1
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐶 ∈ (𝐴[,]𝐵) ↔ -𝐶 ∈ (-𝐵[,]-𝐴))) |