| Step | Hyp | Ref
 | Expression | 
| 1 |   | omfnex 6507 | 
. . . 4
⊢ (𝐴 ∈ On → (𝑦 ∈ V ↦ (𝑦 +o 𝐴)) Fn V) | 
| 2 |   | 0elon 4427 | 
. . . . 5
⊢ ∅
∈ On | 
| 3 |   | rdgival 6440 | 
. . . . 5
⊢ (((𝑦 ∈ V ↦ (𝑦 +o 𝐴)) Fn V ∧ ∅ ∈ On ∧ 𝐵 ∈ On) → (rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝐵) = (∅ ∪ ∪ 𝑥 ∈ 𝐵 ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥)))) | 
| 4 | 2, 3 | mp3an2 1336 | 
. . . 4
⊢ (((𝑦 ∈ V ↦ (𝑦 +o 𝐴)) Fn V ∧ 𝐵 ∈ On) → (rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝐵) = (∅ ∪ ∪ 𝑥 ∈ 𝐵 ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥)))) | 
| 5 | 1, 4 | sylan 283 | 
. . 3
⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝐵) = (∅ ∪ ∪ 𝑥 ∈ 𝐵 ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥)))) | 
| 6 |   | omv 6513 | 
. . 3
⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 ·o 𝐵) = (rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝐵)) | 
| 7 |   | onelon 4419 | 
. . . . . . 7
⊢ ((𝐵 ∈ On ∧ 𝑥 ∈ 𝐵) → 𝑥 ∈ On) | 
| 8 |   | omexg 6509 | 
. . . . . . . . 9
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → (𝐴 ·o 𝑥) ∈ V) | 
| 9 |   | omcl 6519 | 
. . . . . . . . . 10
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → (𝐴 ·o 𝑥) ∈ On) | 
| 10 |   | simpl 109 | 
. . . . . . . . . 10
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → 𝐴 ∈ On) | 
| 11 |   | oacl 6518 | 
. . . . . . . . . 10
⊢ (((𝐴 ·o 𝑥) ∈ On ∧ 𝐴 ∈ On) → ((𝐴 ·o 𝑥) +o 𝐴) ∈ On) | 
| 12 | 9, 10, 11 | syl2anc 411 | 
. . . . . . . . 9
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → ((𝐴 ·o 𝑥) +o 𝐴) ∈ On) | 
| 13 |   | oveq1 5929 | 
. . . . . . . . . 10
⊢ (𝑦 = (𝐴 ·o 𝑥) → (𝑦 +o 𝐴) = ((𝐴 ·o 𝑥) +o 𝐴)) | 
| 14 |   | eqid 2196 | 
. . . . . . . . . 10
⊢ (𝑦 ∈ V ↦ (𝑦 +o 𝐴)) = (𝑦 ∈ V ↦ (𝑦 +o 𝐴)) | 
| 15 | 13, 14 | fvmptg 5637 | 
. . . . . . . . 9
⊢ (((𝐴 ·o 𝑥) ∈ V ∧ ((𝐴 ·o 𝑥) +o 𝐴) ∈ On) → ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(𝐴 ·o 𝑥)) = ((𝐴 ·o 𝑥) +o 𝐴)) | 
| 16 | 8, 12, 15 | syl2anc 411 | 
. . . . . . . 8
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(𝐴 ·o 𝑥)) = ((𝐴 ·o 𝑥) +o 𝐴)) | 
| 17 |   | omv 6513 | 
. . . . . . . . 9
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → (𝐴 ·o 𝑥) = (rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥)) | 
| 18 | 17 | fveq2d 5562 | 
. . . . . . . 8
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(𝐴 ·o 𝑥)) = ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥))) | 
| 19 | 16, 18 | eqtr3d 2231 | 
. . . . . . 7
⊢ ((𝐴 ∈ On ∧ 𝑥 ∈ On) → ((𝐴 ·o 𝑥) +o 𝐴) = ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥))) | 
| 20 | 7, 19 | sylan2 286 | 
. . . . . 6
⊢ ((𝐴 ∈ On ∧ (𝐵 ∈ On ∧ 𝑥 ∈ 𝐵)) → ((𝐴 ·o 𝑥) +o 𝐴) = ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥))) | 
| 21 | 20 | anassrs 400 | 
. . . . 5
⊢ (((𝐴 ∈ On ∧ 𝐵 ∈ On) ∧ 𝑥 ∈ 𝐵) → ((𝐴 ·o 𝑥) +o 𝐴) = ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥))) | 
| 22 | 21 | iuneq2dv 3937 | 
. . . 4
⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → ∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴) = ∪
𝑥 ∈ 𝐵 ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥))) | 
| 23 | 22 | uneq2d 3317 | 
. . 3
⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (∅
∪ ∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴)) = (∅ ∪ ∪ 𝑥 ∈ 𝐵 ((𝑦 ∈ V ↦ (𝑦 +o 𝐴))‘(rec((𝑦 ∈ V ↦ (𝑦 +o 𝐴)), ∅)‘𝑥)))) | 
| 24 | 5, 6, 23 | 3eqtr4d 2239 | 
. 2
⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 ·o 𝐵) = (∅ ∪ ∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴))) | 
| 25 |   | uncom 3307 | 
. . 3
⊢ (∅
∪ ∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴)) = (∪
𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴) ∪ ∅) | 
| 26 |   | un0 3484 | 
. . 3
⊢ (∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴) ∪ ∅) = ∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴) | 
| 27 | 25, 26 | eqtri 2217 | 
. 2
⊢ (∅
∪ ∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴)) = ∪
𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴) | 
| 28 | 24, 27 | eqtrdi 2245 | 
1
⊢ ((𝐴 ∈ On ∧ 𝐵 ∈ On) → (𝐴 ·o 𝐵) = ∪ 𝑥 ∈ 𝐵 ((𝐴 ·o 𝑥) +o 𝐴)) |