Proof of Theorem tfrcllemssrecs
| Step | Hyp | Ref
 | Expression | 
| 1 |   | tfrcllemssrecs.1 | 
. . . 4
⊢ 𝐴 = {𝑓 ∣ ∃𝑥 ∈ 𝑋 (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} | 
| 2 |   | tfrcllemssrecs.x | 
. . . . . 6
⊢ (𝜑 → Ord 𝑋) | 
| 3 |   | ordsson 4528 | 
. . . . . 6
⊢ (Ord
𝑋 → 𝑋 ⊆ On) | 
| 4 |   | ssrexv 3248 | 
. . . . . 6
⊢ (𝑋 ⊆ On → (∃𝑥 ∈ 𝑋 (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦))) → ∃𝑥 ∈ On (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦))))) | 
| 5 | 2, 3, 4 | 3syl 17 | 
. . . . 5
⊢ (𝜑 → (∃𝑥 ∈ 𝑋 (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦))) → ∃𝑥 ∈ On (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦))))) | 
| 6 | 5 | ss2abdv 3256 | 
. . . 4
⊢ (𝜑 → {𝑓 ∣ ∃𝑥 ∈ 𝑋 (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} ⊆ {𝑓 ∣ ∃𝑥 ∈ On (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))}) | 
| 7 | 1, 6 | eqsstrid 3229 | 
. . 3
⊢ (𝜑 → 𝐴 ⊆ {𝑓 ∣ ∃𝑥 ∈ On (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))}) | 
| 8 | 7 | unissd 3863 | 
. 2
⊢ (𝜑 → ∪ 𝐴
⊆ ∪ {𝑓 ∣ ∃𝑥 ∈ On (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))}) | 
| 9 |   | ffn 5407 | 
. . . . . . 7
⊢ (𝑓:𝑥⟶𝑆 → 𝑓 Fn 𝑥) | 
| 10 | 9 | anim1i 340 | 
. . . . . 6
⊢ ((𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦))) → (𝑓 Fn 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))) | 
| 11 | 10 | reximi 2594 | 
. . . . 5
⊢
(∃𝑥 ∈ On
(𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦))) → ∃𝑥 ∈ On (𝑓 Fn 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))) | 
| 12 | 11 | ss2abi 3255 | 
. . . 4
⊢ {𝑓 ∣ ∃𝑥 ∈ On (𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} ⊆ {𝑓 ∣ ∃𝑥 ∈ On (𝑓 Fn 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} | 
| 13 | 12 | unissi 3862 | 
. . 3
⊢ ∪ {𝑓
∣ ∃𝑥 ∈ On
(𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} ⊆ ∪
{𝑓 ∣ ∃𝑥 ∈ On (𝑓 Fn 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} | 
| 14 |   | df-recs 6363 | 
. . 3
⊢
recs(𝐺) = ∪ {𝑓
∣ ∃𝑥 ∈ On
(𝑓 Fn 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} | 
| 15 | 13, 14 | sseqtrri 3218 | 
. 2
⊢ ∪ {𝑓
∣ ∃𝑥 ∈ On
(𝑓:𝑥⟶𝑆 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} ⊆ recs(𝐺) | 
| 16 | 8, 15 | sstrdi 3195 | 
1
⊢ (𝜑 → ∪ 𝐴
⊆ recs(𝐺)) |