Proof of Theorem nninfisollemne
| Step | Hyp | Ref
 | Expression | 
| 1 |   | nninfisollemne.0 | 
. . . . 5
⊢ (𝜑 → (𝑋‘∪ 𝑁) = ∅) | 
| 2 | 1 | adantr 276 | 
. . . 4
⊢ ((𝜑 ∧ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) → (𝑋‘∪ 𝑁) = ∅) | 
| 3 |   | simpr 110 | 
. . . . . . . 8
⊢ ((𝜑 ∧ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) → (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) | 
| 4 | 3 | fveq1d 5560 | 
. . . . . . 7
⊢ ((𝜑 ∧ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) → ((𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅))‘∪ 𝑁) =
(𝑋‘∪ 𝑁)) | 
| 5 |   | eqid 2196 | 
. . . . . . . . . 10
⊢ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) | 
| 6 |   | eleq1 2259 | 
. . . . . . . . . . 11
⊢ (𝑖 = ∪
𝑁 → (𝑖 ∈ 𝑁 ↔ ∪ 𝑁 ∈ 𝑁)) | 
| 7 | 6 | ifbid 3582 | 
. . . . . . . . . 10
⊢ (𝑖 = ∪
𝑁 → if(𝑖 ∈ 𝑁, 1o, ∅) = if(∪ 𝑁
∈ 𝑁, 1o,
∅)) | 
| 8 |   | nninfisol.n | 
. . . . . . . . . . 11
⊢ (𝜑 → 𝑁 ∈ ω) | 
| 9 |   | nnpredcl 4659 | 
. . . . . . . . . . 11
⊢ (𝑁 ∈ ω → ∪ 𝑁
∈ ω) | 
| 10 | 8, 9 | syl 14 | 
. . . . . . . . . 10
⊢ (𝜑 → ∪ 𝑁
∈ ω) | 
| 11 |   | nninfisollemne.s | 
. . . . . . . . . . . . 13
⊢ (𝜑 → 𝑁 ≠ ∅) | 
| 12 |   | nnpredlt 4660 | 
. . . . . . . . . . . . 13
⊢ ((𝑁 ∈ ω ∧ 𝑁 ≠ ∅) → ∪ 𝑁
∈ 𝑁) | 
| 13 | 8, 11, 12 | syl2anc 411 | 
. . . . . . . . . . . 12
⊢ (𝜑 → ∪ 𝑁
∈ 𝑁) | 
| 14 | 13 | iftrued 3568 | 
. . . . . . . . . . 11
⊢ (𝜑 → if(∪ 𝑁
∈ 𝑁, 1o,
∅) = 1o) | 
| 15 |   | 1lt2o 6500 | 
. . . . . . . . . . 11
⊢
1o ∈ 2o | 
| 16 | 14, 15 | eqeltrdi 2287 | 
. . . . . . . . . 10
⊢ (𝜑 → if(∪ 𝑁
∈ 𝑁, 1o,
∅) ∈ 2o) | 
| 17 | 5, 7, 10, 16 | fvmptd3 5655 | 
. . . . . . . . 9
⊢ (𝜑 → ((𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅))‘∪ 𝑁) =
if(∪ 𝑁 ∈ 𝑁, 1o, ∅)) | 
| 18 | 17, 14 | eqtrd 2229 | 
. . . . . . . 8
⊢ (𝜑 → ((𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅))‘∪ 𝑁) =
1o) | 
| 19 | 18 | adantr 276 | 
. . . . . . 7
⊢ ((𝜑 ∧ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) → ((𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅))‘∪ 𝑁) =
1o) | 
| 20 | 4, 19 | eqtr3d 2231 | 
. . . . . 6
⊢ ((𝜑 ∧ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) → (𝑋‘∪ 𝑁) =
1o) | 
| 21 |   | 1n0 6490 | 
. . . . . 6
⊢
1o ≠ ∅ | 
| 22 |   | pm13.181 2449 | 
. . . . . 6
⊢ (((𝑋‘∪ 𝑁) =
1o ∧ 1o ≠ ∅) → (𝑋‘∪ 𝑁) ≠ ∅) | 
| 23 | 20, 21, 22 | sylancl 413 | 
. . . . 5
⊢ ((𝜑 ∧ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) → (𝑋‘∪ 𝑁) ≠ ∅) | 
| 24 | 23 | neneqd 2388 | 
. . . 4
⊢ ((𝜑 ∧ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) → ¬ (𝑋‘∪ 𝑁) =
∅) | 
| 25 | 2, 24 | pm2.65da 662 | 
. . 3
⊢ (𝜑 → ¬ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋) | 
| 26 | 25 | olcd 735 | 
. 2
⊢ (𝜑 → ((𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋 ∨ ¬ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋)) | 
| 27 |   | df-dc 836 | 
. 2
⊢
(DECID (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋 ↔ ((𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋 ∨ ¬ (𝑖 ∈ ω ↦ if(𝑖 ∈ 𝑁, 1o, ∅)) = 𝑋)) | 
| 28 | 26, 27 | sylibr 134 | 
1
⊢ (𝜑 → DECID
(𝑖 ∈ ω ↦
if(𝑖 ∈ 𝑁, 1o, ∅)) =
𝑋) |