Proof of Theorem xrmaxifle
| Step | Hyp | Ref
 | Expression | 
| 1 |   | pnfge 9864 | 
. . . 4
⊢ (𝐴 ∈ ℝ*
→ 𝐴 ≤
+∞) | 
| 2 | 1 | ad2antrr 488 | 
. . 3
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ 𝐵 = +∞) → 𝐴 ≤ +∞) | 
| 3 |   | simpr 110 | 
. . . 4
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ 𝐵 = +∞) → 𝐵 = +∞) | 
| 4 | 3 | iftrued 3568 | 
. . 3
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ 𝐵 = +∞) → if(𝐵 = +∞, +∞, if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))))) =
+∞) | 
| 5 | 2, 4 | breqtrrd 4061 | 
. 2
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ 𝐵 = +∞) → 𝐴 ≤ if(𝐵 = +∞, +∞, if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))))) | 
| 6 |   | xrleid 9875 | 
. . . . . 6
⊢ (𝐴 ∈ ℝ*
→ 𝐴 ≤ 𝐴) | 
| 7 | 6 | ad3antrrr 492 | 
. . . . 5
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ 𝐵 = -∞) → 𝐴 ≤ 𝐴) | 
| 8 |   | simpr 110 | 
. . . . . 6
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ 𝐵 = -∞) → 𝐵 = -∞) | 
| 9 | 8 | iftrued 3568 | 
. . . . 5
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ 𝐵 = -∞) → if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))) = 𝐴) | 
| 10 | 7, 9 | breqtrrd 4061 | 
. . . 4
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ 𝐵 = -∞) → 𝐴 ≤ if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))))) | 
| 11 | 1 | ad4antr 494 | 
. . . . . . 7
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ 𝐴 = +∞) → 𝐴 ≤ +∞) | 
| 12 |   | simpr 110 | 
. . . . . . . 8
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ 𝐴 = +∞) → 𝐴 = +∞) | 
| 13 | 12 | iftrued 3568 | 
. . . . . . 7
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ 𝐴 = +∞) → if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))) =
+∞) | 
| 14 | 11, 13 | breqtrrd 4061 | 
. . . . . 6
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ 𝐴 = +∞) → 𝐴 ≤ if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))) | 
| 15 |   | mnfle 9867 | 
. . . . . . . . . 10
⊢ (𝐵 ∈ ℝ*
→ -∞ ≤ 𝐵) | 
| 16 | 15 | ad5antlr 497 | 
. . . . . . . . 9
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ 𝐴 = -∞) → -∞ ≤ 𝐵) | 
| 17 |   | simpr 110 | 
. . . . . . . . 9
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ 𝐴 = -∞) → 𝐴 = -∞) | 
| 18 | 17 | iftrued 3568 | 
. . . . . . . . 9
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ 𝐴 = -∞) → if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )) = 𝐵) | 
| 19 | 16, 17, 18 | 3brtr4d 4065 | 
. . . . . . . 8
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ 𝐴 = -∞) → 𝐴 ≤ if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))) | 
| 20 |   | simplr 528 | 
. . . . . . . . . . 11
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → ¬ 𝐴 = +∞) | 
| 21 |   | simpr 110 | 
. . . . . . . . . . 11
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → ¬ 𝐴 = -∞) | 
| 22 |   | elxr 9851 | 
. . . . . . . . . . . . 13
⊢ (𝐴 ∈ ℝ*
↔ (𝐴 ∈ ℝ
∨ 𝐴 = +∞ ∨
𝐴 =
-∞)) | 
| 23 | 22 | biimpi 120 | 
. . . . . . . . . . . 12
⊢ (𝐴 ∈ ℝ*
→ (𝐴 ∈ ℝ
∨ 𝐴 = +∞ ∨
𝐴 =
-∞)) | 
| 24 | 23 | ad5antr 496 | 
. . . . . . . . . . 11
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → (𝐴 ∈ ℝ ∨ 𝐴 = +∞ ∨ 𝐴 = -∞)) | 
| 25 | 20, 21, 24 | ecase23d 1361 | 
. . . . . . . . . 10
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → 𝐴 ∈ ℝ) | 
| 26 |   | simpr 110 | 
. . . . . . . . . . . 12
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) → ¬ 𝐵 = +∞) | 
| 27 | 26 | ad3antrrr 492 | 
. . . . . . . . . . 11
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → ¬ 𝐵 = +∞) | 
| 28 |   | simpr 110 | 
. . . . . . . . . . . 12
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) → ¬ 𝐵 = -∞) | 
| 29 | 28 | ad2antrr 488 | 
. . . . . . . . . . 11
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → ¬ 𝐵 = -∞) | 
| 30 |   | elxr 9851 | 
. . . . . . . . . . . . 13
⊢ (𝐵 ∈ ℝ*
↔ (𝐵 ∈ ℝ
∨ 𝐵 = +∞ ∨
𝐵 =
-∞)) | 
| 31 | 30 | biimpi 120 | 
. . . . . . . . . . . 12
⊢ (𝐵 ∈ ℝ*
→ (𝐵 ∈ ℝ
∨ 𝐵 = +∞ ∨
𝐵 =
-∞)) | 
| 32 | 31 | ad5antlr 497 | 
. . . . . . . . . . 11
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → (𝐵 ∈ ℝ ∨ 𝐵 = +∞ ∨ 𝐵 = -∞)) | 
| 33 | 27, 29, 32 | ecase23d 1361 | 
. . . . . . . . . 10
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → 𝐵 ∈ ℝ) | 
| 34 |   | maxle1 11376 | 
. . . . . . . . . 10
⊢ ((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → 𝐴 ≤ sup({𝐴, 𝐵}, ℝ, < )) | 
| 35 | 25, 33, 34 | syl2anc 411 | 
. . . . . . . . 9
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → 𝐴 ≤ sup({𝐴, 𝐵}, ℝ, < )) | 
| 36 | 21 | iffalsed 3571 | 
. . . . . . . . 9
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )) = sup({𝐴, 𝐵}, ℝ, < )) | 
| 37 | 35, 36 | breqtrrd 4061 | 
. . . . . . . 8
⊢
((((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) ∧ ¬ 𝐴 = -∞) → 𝐴 ≤ if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))) | 
| 38 |   | xrmnfdc 9918 | 
. . . . . . . . . 10
⊢ (𝐴 ∈ ℝ*
→ DECID 𝐴 = -∞) | 
| 39 |   | exmiddc 837 | 
. . . . . . . . . 10
⊢
(DECID 𝐴 = -∞ → (𝐴 = -∞ ∨ ¬ 𝐴 = -∞)) | 
| 40 | 38, 39 | syl 14 | 
. . . . . . . . 9
⊢ (𝐴 ∈ ℝ*
→ (𝐴 = -∞ ∨
¬ 𝐴 =
-∞)) | 
| 41 | 40 | ad4antr 494 | 
. . . . . . . 8
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) → (𝐴 = -∞ ∨ ¬ 𝐴 = -∞)) | 
| 42 | 19, 37, 41 | mpjaodan 799 | 
. . . . . . 7
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) → 𝐴 ≤ if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))) | 
| 43 |   | simpr 110 | 
. . . . . . . 8
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) → ¬ 𝐴 = +∞) | 
| 44 | 43 | iffalsed 3571 | 
. . . . . . 7
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) → if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))) = if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))) | 
| 45 | 42, 44 | breqtrrd 4061 | 
. . . . . 6
⊢
(((((𝐴 ∈
ℝ* ∧ 𝐵
∈ ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) ∧ ¬ 𝐴 = +∞) → 𝐴 ≤ if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))) | 
| 46 |   | xrpnfdc 9917 | 
. . . . . . . 8
⊢ (𝐴 ∈ ℝ*
→ DECID 𝐴 = +∞) | 
| 47 |   | exmiddc 837 | 
. . . . . . . 8
⊢
(DECID 𝐴 = +∞ → (𝐴 = +∞ ∨ ¬ 𝐴 = +∞)) | 
| 48 | 46, 47 | syl 14 | 
. . . . . . 7
⊢ (𝐴 ∈ ℝ*
→ (𝐴 = +∞ ∨
¬ 𝐴 =
+∞)) | 
| 49 | 48 | ad3antrrr 492 | 
. . . . . 6
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) → (𝐴 = +∞ ∨ ¬ 𝐴 = +∞)) | 
| 50 | 14, 45, 49 | mpjaodan 799 | 
. . . . 5
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) → 𝐴 ≤ if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))) | 
| 51 | 28 | iffalsed 3571 | 
. . . . 5
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) → if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))) = if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))) | 
| 52 | 50, 51 | breqtrrd 4061 | 
. . . 4
⊢ ((((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) ∧ ¬ 𝐵 = -∞) → 𝐴 ≤ if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))))) | 
| 53 |   | xrmnfdc 9918 | 
. . . . . 6
⊢ (𝐵 ∈ ℝ*
→ DECID 𝐵 = -∞) | 
| 54 |   | exmiddc 837 | 
. . . . . 6
⊢
(DECID 𝐵 = -∞ → (𝐵 = -∞ ∨ ¬ 𝐵 = -∞)) | 
| 55 | 53, 54 | syl 14 | 
. . . . 5
⊢ (𝐵 ∈ ℝ*
→ (𝐵 = -∞ ∨
¬ 𝐵 =
-∞)) | 
| 56 | 55 | ad2antlr 489 | 
. . . 4
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) → (𝐵 = -∞ ∨ ¬ 𝐵 = -∞)) | 
| 57 | 10, 52, 56 | mpjaodan 799 | 
. . 3
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) → 𝐴 ≤ if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))))) | 
| 58 | 26 | iffalsed 3571 | 
. . 3
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) → if(𝐵 = +∞, +∞, if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))))) = if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < ))))) | 
| 59 | 57, 58 | breqtrrd 4061 | 
. 2
⊢ (((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) ∧ ¬ 𝐵 = +∞) → 𝐴 ≤ if(𝐵 = +∞, +∞, if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))))) | 
| 60 |   | xrpnfdc 9917 | 
. . . 4
⊢ (𝐵 ∈ ℝ*
→ DECID 𝐵 = +∞) | 
| 61 |   | exmiddc 837 | 
. . . 4
⊢
(DECID 𝐵 = +∞ → (𝐵 = +∞ ∨ ¬ 𝐵 = +∞)) | 
| 62 | 60, 61 | syl 14 | 
. . 3
⊢ (𝐵 ∈ ℝ*
→ (𝐵 = +∞ ∨
¬ 𝐵 =
+∞)) | 
| 63 | 62 | adantl 277 | 
. 2
⊢ ((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) → (𝐵 = +∞ ∨ ¬ 𝐵 = +∞)) | 
| 64 | 5, 59, 63 | mpjaodan 799 | 
1
⊢ ((𝐴 ∈ ℝ*
∧ 𝐵 ∈
ℝ*) → 𝐴 ≤ if(𝐵 = +∞, +∞, if(𝐵 = -∞, 𝐴, if(𝐴 = +∞, +∞, if(𝐴 = -∞, 𝐵, sup({𝐴, 𝐵}, ℝ, < )))))) |