Proof of Theorem fnn0ind
| Step | Hyp | Ref
 | Expression | 
| 1 |   | elnn0z 9339 | 
. . . 4
⊢ (𝐾 ∈ ℕ0
↔ (𝐾 ∈ ℤ
∧ 0 ≤ 𝐾)) | 
| 2 |   | nn0z 9346 | 
. . . . . 6
⊢ (𝑁 ∈ ℕ0
→ 𝑁 ∈
ℤ) | 
| 3 |   | 0z 9337 | 
. . . . . . . 8
⊢ 0 ∈
ℤ | 
| 4 |   | fnn0ind.1 | 
. . . . . . . . 9
⊢ (𝑥 = 0 → (𝜑 ↔ 𝜓)) | 
| 5 |   | fnn0ind.2 | 
. . . . . . . . 9
⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜒)) | 
| 6 |   | fnn0ind.3 | 
. . . . . . . . 9
⊢ (𝑥 = (𝑦 + 1) → (𝜑 ↔ 𝜃)) | 
| 7 |   | fnn0ind.4 | 
. . . . . . . . 9
⊢ (𝑥 = 𝐾 → (𝜑 ↔ 𝜏)) | 
| 8 |   | elnn0z 9339 | 
. . . . . . . . . . 11
⊢ (𝑁 ∈ ℕ0
↔ (𝑁 ∈ ℤ
∧ 0 ≤ 𝑁)) | 
| 9 |   | fnn0ind.5 | 
. . . . . . . . . . 11
⊢ (𝑁 ∈ ℕ0
→ 𝜓) | 
| 10 | 8, 9 | sylbir 135 | 
. . . . . . . . . 10
⊢ ((𝑁 ∈ ℤ ∧ 0 ≤
𝑁) → 𝜓) | 
| 11 | 10 | 3adant1 1017 | 
. . . . . . . . 9
⊢ ((0
∈ ℤ ∧ 𝑁
∈ ℤ ∧ 0 ≤ 𝑁) → 𝜓) | 
| 12 |   | zre 9330 | 
. . . . . . . . . . . . . . . 16
⊢ (𝑦 ∈ ℤ → 𝑦 ∈
ℝ) | 
| 13 |   | zre 9330 | 
. . . . . . . . . . . . . . . 16
⊢ (𝑁 ∈ ℤ → 𝑁 ∈
ℝ) | 
| 14 |   | 0re 8026 | 
. . . . . . . . . . . . . . . . 17
⊢ 0 ∈
ℝ | 
| 15 |   | lelttr 8115 | 
. . . . . . . . . . . . . . . . . 18
⊢ ((0
∈ ℝ ∧ 𝑦
∈ ℝ ∧ 𝑁
∈ ℝ) → ((0 ≤ 𝑦 ∧ 𝑦 < 𝑁) → 0 < 𝑁)) | 
| 16 |   | ltle 8114 | 
. . . . . . . . . . . . . . . . . . 19
⊢ ((0
∈ ℝ ∧ 𝑁
∈ ℝ) → (0 < 𝑁 → 0 ≤ 𝑁)) | 
| 17 | 16 | 3adant2 1018 | 
. . . . . . . . . . . . . . . . . 18
⊢ ((0
∈ ℝ ∧ 𝑦
∈ ℝ ∧ 𝑁
∈ ℝ) → (0 < 𝑁 → 0 ≤ 𝑁)) | 
| 18 | 15, 17 | syld 45 | 
. . . . . . . . . . . . . . . . 17
⊢ ((0
∈ ℝ ∧ 𝑦
∈ ℝ ∧ 𝑁
∈ ℝ) → ((0 ≤ 𝑦 ∧ 𝑦 < 𝑁) → 0 ≤ 𝑁)) | 
| 19 | 14, 18 | mp3an1 1335 | 
. . . . . . . . . . . . . . . 16
⊢ ((𝑦 ∈ ℝ ∧ 𝑁 ∈ ℝ) → ((0 ≤
𝑦 ∧ 𝑦 < 𝑁) → 0 ≤ 𝑁)) | 
| 20 | 12, 13, 19 | syl2an 289 | 
. . . . . . . . . . . . . . 15
⊢ ((𝑦 ∈ ℤ ∧ 𝑁 ∈ ℤ) → ((0 ≤
𝑦 ∧ 𝑦 < 𝑁) → 0 ≤ 𝑁)) | 
| 21 | 20 | ex 115 | 
. . . . . . . . . . . . . 14
⊢ (𝑦 ∈ ℤ → (𝑁 ∈ ℤ → ((0 ≤
𝑦 ∧ 𝑦 < 𝑁) → 0 ≤ 𝑁))) | 
| 22 | 21 | com23 78 | 
. . . . . . . . . . . . 13
⊢ (𝑦 ∈ ℤ → ((0 ≤
𝑦 ∧ 𝑦 < 𝑁) → (𝑁 ∈ ℤ → 0 ≤ 𝑁))) | 
| 23 | 22 | 3impib 1203 | 
. . . . . . . . . . . 12
⊢ ((𝑦 ∈ ℤ ∧ 0 ≤
𝑦 ∧ 𝑦 < 𝑁) → (𝑁 ∈ ℤ → 0 ≤ 𝑁)) | 
| 24 | 23 | impcom 125 | 
. . . . . . . . . . 11
⊢ ((𝑁 ∈ ℤ ∧ (𝑦 ∈ ℤ ∧ 0 ≤
𝑦 ∧ 𝑦 < 𝑁)) → 0 ≤ 𝑁) | 
| 25 |   | elnn0z 9339 | 
. . . . . . . . . . . . . . . . 17
⊢ (𝑦 ∈ ℕ0
↔ (𝑦 ∈ ℤ
∧ 0 ≤ 𝑦)) | 
| 26 | 25 | anbi1i 458 | 
. . . . . . . . . . . . . . . 16
⊢ ((𝑦 ∈ ℕ0
∧ 𝑦 < 𝑁) ↔ ((𝑦 ∈ ℤ ∧ 0 ≤ 𝑦) ∧ 𝑦 < 𝑁)) | 
| 27 |   | fnn0ind.6 | 
. . . . . . . . . . . . . . . . 17
⊢ ((𝑁 ∈ ℕ0
∧ 𝑦 ∈
ℕ0 ∧ 𝑦
< 𝑁) → (𝜒 → 𝜃)) | 
| 28 | 27 | 3expb 1206 | 
. . . . . . . . . . . . . . . 16
⊢ ((𝑁 ∈ ℕ0
∧ (𝑦 ∈
ℕ0 ∧ 𝑦
< 𝑁)) → (𝜒 → 𝜃)) | 
| 29 | 8, 26, 28 | syl2anbr 292 | 
. . . . . . . . . . . . . . 15
⊢ (((𝑁 ∈ ℤ ∧ 0 ≤
𝑁) ∧ ((𝑦 ∈ ℤ ∧ 0 ≤
𝑦) ∧ 𝑦 < 𝑁)) → (𝜒 → 𝜃)) | 
| 30 | 29 | expcom 116 | 
. . . . . . . . . . . . . 14
⊢ (((𝑦 ∈ ℤ ∧ 0 ≤
𝑦) ∧ 𝑦 < 𝑁) → ((𝑁 ∈ ℤ ∧ 0 ≤ 𝑁) → (𝜒 → 𝜃))) | 
| 31 | 30 | 3impa 1196 | 
. . . . . . . . . . . . 13
⊢ ((𝑦 ∈ ℤ ∧ 0 ≤
𝑦 ∧ 𝑦 < 𝑁) → ((𝑁 ∈ ℤ ∧ 0 ≤ 𝑁) → (𝜒 → 𝜃))) | 
| 32 | 31 | expd 258 | 
. . . . . . . . . . . 12
⊢ ((𝑦 ∈ ℤ ∧ 0 ≤
𝑦 ∧ 𝑦 < 𝑁) → (𝑁 ∈ ℤ → (0 ≤ 𝑁 → (𝜒 → 𝜃)))) | 
| 33 | 32 | impcom 125 | 
. . . . . . . . . . 11
⊢ ((𝑁 ∈ ℤ ∧ (𝑦 ∈ ℤ ∧ 0 ≤
𝑦 ∧ 𝑦 < 𝑁)) → (0 ≤ 𝑁 → (𝜒 → 𝜃))) | 
| 34 | 24, 33 | mpd 13 | 
. . . . . . . . . 10
⊢ ((𝑁 ∈ ℤ ∧ (𝑦 ∈ ℤ ∧ 0 ≤
𝑦 ∧ 𝑦 < 𝑁)) → (𝜒 → 𝜃)) | 
| 35 | 34 | adantll 476 | 
. . . . . . . . 9
⊢ (((0
∈ ℤ ∧ 𝑁
∈ ℤ) ∧ (𝑦
∈ ℤ ∧ 0 ≤ 𝑦 ∧ 𝑦 < 𝑁)) → (𝜒 → 𝜃)) | 
| 36 | 4, 5, 6, 7, 11, 35 | fzind 9441 | 
. . . . . . . 8
⊢ (((0
∈ ℤ ∧ 𝑁
∈ ℤ) ∧ (𝐾
∈ ℤ ∧ 0 ≤ 𝐾 ∧ 𝐾 ≤ 𝑁)) → 𝜏) | 
| 37 | 3, 36 | mpanl1 434 | 
. . . . . . 7
⊢ ((𝑁 ∈ ℤ ∧ (𝐾 ∈ ℤ ∧ 0 ≤
𝐾 ∧ 𝐾 ≤ 𝑁)) → 𝜏) | 
| 38 | 37 | expcom 116 | 
. . . . . 6
⊢ ((𝐾 ∈ ℤ ∧ 0 ≤
𝐾 ∧ 𝐾 ≤ 𝑁) → (𝑁 ∈ ℤ → 𝜏)) | 
| 39 | 2, 38 | syl5 32 | 
. . . . 5
⊢ ((𝐾 ∈ ℤ ∧ 0 ≤
𝐾 ∧ 𝐾 ≤ 𝑁) → (𝑁 ∈ ℕ0 → 𝜏)) | 
| 40 | 39 | 3expa 1205 | 
. . . 4
⊢ (((𝐾 ∈ ℤ ∧ 0 ≤
𝐾) ∧ 𝐾 ≤ 𝑁) → (𝑁 ∈ ℕ0 → 𝜏)) | 
| 41 | 1, 40 | sylanb 284 | 
. . 3
⊢ ((𝐾 ∈ ℕ0
∧ 𝐾 ≤ 𝑁) → (𝑁 ∈ ℕ0 → 𝜏)) | 
| 42 | 41 | impcom 125 | 
. 2
⊢ ((𝑁 ∈ ℕ0
∧ (𝐾 ∈
ℕ0 ∧ 𝐾
≤ 𝑁)) → 𝜏) | 
| 43 | 42 | 3impb 1201 | 
1
⊢ ((𝑁 ∈ ℕ0
∧ 𝐾 ∈
ℕ0 ∧ 𝐾
≤ 𝑁) → 𝜏) |