| Step | Hyp | Ref
 | Expression | 
| 1 |   | elfzelz 10100 | 
. . 3
⊢ (𝑘 ∈ (𝑀...𝑁) → 𝑘 ∈ ℤ) | 
| 2 | 1 | adantl 277 | 
. 2
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ (𝑀...𝑁)) → 𝑘 ∈ ℤ) | 
| 3 |   | eldifi 3285 | 
. . . 4
⊢ (𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}) → 𝑘 ∈ (𝑀...(𝑁 + 1))) | 
| 4 |   | elfzelz 10100 | 
. . . 4
⊢ (𝑘 ∈ (𝑀...(𝑁 + 1)) → 𝑘 ∈ ℤ) | 
| 5 | 3, 4 | syl 14 | 
. . 3
⊢ (𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}) → 𝑘 ∈ ℤ) | 
| 6 | 5 | adantl 277 | 
. 2
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)})) → 𝑘 ∈ ℤ) | 
| 7 |   | simpr 110 | 
. . . 4
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → 𝑘 ∈ ℤ) | 
| 8 |   | eluzel2 9606 | 
. . . . 5
⊢ (𝑁 ∈
(ℤ≥‘𝑀) → 𝑀 ∈ ℤ) | 
| 9 | 8 | adantr 276 | 
. . . 4
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → 𝑀 ∈ ℤ) | 
| 10 |   | eluzelz 9610 | 
. . . . 5
⊢ (𝑁 ∈
(ℤ≥‘𝑀) → 𝑁 ∈ ℤ) | 
| 11 | 10 | adantr 276 | 
. . . 4
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → 𝑁 ∈ ℤ) | 
| 12 |   | elfz 10089 | 
. . . 4
⊢ ((𝑘 ∈ ℤ ∧ 𝑀 ∈ ℤ ∧ 𝑁 ∈ ℤ) → (𝑘 ∈ (𝑀...𝑁) ↔ (𝑀 ≤ 𝑘 ∧ 𝑘 ≤ 𝑁))) | 
| 13 | 7, 9, 11, 12 | syl3anc 1249 | 
. . 3
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ∈ (𝑀...𝑁) ↔ (𝑀 ≤ 𝑘 ∧ 𝑘 ≤ 𝑁))) | 
| 14 |   | eldif 3166 | 
. . . . . . 7
⊢ (𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}) ↔ (𝑘 ∈ (𝑀...(𝑁 + 1)) ∧ ¬ 𝑘 ∈ {(𝑁 + 1)})) | 
| 15 | 11 | peano2zd 9451 | 
. . . . . . . . 9
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑁 + 1) ∈ ℤ) | 
| 16 |   | elfz 10089 | 
. . . . . . . . 9
⊢ ((𝑘 ∈ ℤ ∧ 𝑀 ∈ ℤ ∧ (𝑁 + 1) ∈ ℤ) →
(𝑘 ∈ (𝑀...(𝑁 + 1)) ↔ (𝑀 ≤ 𝑘 ∧ 𝑘 ≤ (𝑁 + 1)))) | 
| 17 | 7, 9, 15, 16 | syl3anc 1249 | 
. . . . . . . 8
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ∈ (𝑀...(𝑁 + 1)) ↔ (𝑀 ≤ 𝑘 ∧ 𝑘 ≤ (𝑁 + 1)))) | 
| 18 |   | velsn 3639 | 
. . . . . . . . . . 11
⊢ (𝑘 ∈ {(𝑁 + 1)} ↔ 𝑘 = (𝑁 + 1)) | 
| 19 | 18 | notbii 669 | 
. . . . . . . . . 10
⊢ (¬
𝑘 ∈ {(𝑁 + 1)} ↔ ¬ 𝑘 = (𝑁 + 1)) | 
| 20 |   | nesym 2412 | 
. . . . . . . . . 10
⊢ ((𝑁 + 1) ≠ 𝑘 ↔ ¬ 𝑘 = (𝑁 + 1)) | 
| 21 | 19, 20 | bitr4i 187 | 
. . . . . . . . 9
⊢ (¬
𝑘 ∈ {(𝑁 + 1)} ↔ (𝑁 + 1) ≠ 𝑘) | 
| 22 | 21 | a1i 9 | 
. . . . . . . 8
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (¬ 𝑘 ∈ {(𝑁 + 1)} ↔ (𝑁 + 1) ≠ 𝑘)) | 
| 23 | 17, 22 | anbi12d 473 | 
. . . . . . 7
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → ((𝑘 ∈ (𝑀...(𝑁 + 1)) ∧ ¬ 𝑘 ∈ {(𝑁 + 1)}) ↔ ((𝑀 ≤ 𝑘 ∧ 𝑘 ≤ (𝑁 + 1)) ∧ (𝑁 + 1) ≠ 𝑘))) | 
| 24 | 14, 23 | bitrid 192 | 
. . . . . 6
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}) ↔ ((𝑀 ≤ 𝑘 ∧ 𝑘 ≤ (𝑁 + 1)) ∧ (𝑁 + 1) ≠ 𝑘))) | 
| 25 |   | anass 401 | 
. . . . . 6
⊢ (((𝑀 ≤ 𝑘 ∧ 𝑘 ≤ (𝑁 + 1)) ∧ (𝑁 + 1) ≠ 𝑘) ↔ (𝑀 ≤ 𝑘 ∧ (𝑘 ≤ (𝑁 + 1) ∧ (𝑁 + 1) ≠ 𝑘))) | 
| 26 | 24, 25 | bitrdi 196 | 
. . . . 5
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}) ↔ (𝑀 ≤ 𝑘 ∧ (𝑘 ≤ (𝑁 + 1) ∧ (𝑁 + 1) ≠ 𝑘)))) | 
| 27 |   | zltlen 9404 | 
. . . . . . 7
⊢ ((𝑘 ∈ ℤ ∧ (𝑁 + 1) ∈ ℤ) →
(𝑘 < (𝑁 + 1) ↔ (𝑘 ≤ (𝑁 + 1) ∧ (𝑁 + 1) ≠ 𝑘))) | 
| 28 | 7, 15, 27 | syl2anc 411 | 
. . . . . 6
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 < (𝑁 + 1) ↔ (𝑘 ≤ (𝑁 + 1) ∧ (𝑁 + 1) ≠ 𝑘))) | 
| 29 | 28 | anbi2d 464 | 
. . . . 5
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → ((𝑀 ≤ 𝑘 ∧ 𝑘 < (𝑁 + 1)) ↔ (𝑀 ≤ 𝑘 ∧ (𝑘 ≤ (𝑁 + 1) ∧ (𝑁 + 1) ≠ 𝑘)))) | 
| 30 | 26, 29 | bitr4d 191 | 
. . . 4
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}) ↔ (𝑀 ≤ 𝑘 ∧ 𝑘 < (𝑁 + 1)))) | 
| 31 |   | zleltp1 9381 | 
. . . . . 6
⊢ ((𝑘 ∈ ℤ ∧ 𝑁 ∈ ℤ) → (𝑘 ≤ 𝑁 ↔ 𝑘 < (𝑁 + 1))) | 
| 32 | 7, 11, 31 | syl2anc 411 | 
. . . . 5
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ≤ 𝑁 ↔ 𝑘 < (𝑁 + 1))) | 
| 33 | 32 | anbi2d 464 | 
. . . 4
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → ((𝑀 ≤ 𝑘 ∧ 𝑘 ≤ 𝑁) ↔ (𝑀 ≤ 𝑘 ∧ 𝑘 < (𝑁 + 1)))) | 
| 34 | 30, 33 | bitr4d 191 | 
. . 3
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}) ↔ (𝑀 ≤ 𝑘 ∧ 𝑘 ≤ 𝑁))) | 
| 35 | 13, 34 | bitr4d 191 | 
. 2
⊢ ((𝑁 ∈
(ℤ≥‘𝑀) ∧ 𝑘 ∈ ℤ) → (𝑘 ∈ (𝑀...𝑁) ↔ 𝑘 ∈ ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)}))) | 
| 36 | 2, 6, 35 | eqrdav 2195 | 
1
⊢ (𝑁 ∈
(ℤ≥‘𝑀) → (𝑀...𝑁) = ((𝑀...(𝑁 + 1)) ∖ {(𝑁 + 1)})) |