| Step | Hyp | Ref | Expression | 
						
							| 1 |  | onovuni.1 | ⊢ ( Lim  𝑦  →  ( 𝐴 𝐹 𝑦 )  =  ∪  𝑥  ∈  𝑦 ( 𝐴 𝐹 𝑥 ) ) | 
						
							| 2 |  | onovuni.2 | ⊢ ( ( 𝑥  ∈  On  ∧  𝑦  ∈  On  ∧  𝑥  ⊆  𝑦 )  →  ( 𝐴 𝐹 𝑥 )  ⊆  ( 𝐴 𝐹 𝑦 ) ) | 
						
							| 3 |  | oveq2 | ⊢ ( 𝑧  =  𝑦  →  ( 𝐴 𝐹 𝑧 )  =  ( 𝐴 𝐹 𝑦 ) ) | 
						
							| 4 |  | eqid | ⊢ ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) )  =  ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) | 
						
							| 5 |  | ovex | ⊢ ( 𝐴 𝐹 𝑦 )  ∈  V | 
						
							| 6 | 3 4 5 | fvmpt | ⊢ ( 𝑦  ∈  V  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑦 )  =  ( 𝐴 𝐹 𝑦 ) ) | 
						
							| 7 | 6 | elv | ⊢ ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑦 )  =  ( 𝐴 𝐹 𝑦 ) | 
						
							| 8 |  | oveq2 | ⊢ ( 𝑧  =  𝑥  →  ( 𝐴 𝐹 𝑧 )  =  ( 𝐴 𝐹 𝑥 ) ) | 
						
							| 9 |  | ovex | ⊢ ( 𝐴 𝐹 𝑥 )  ∈  V | 
						
							| 10 | 8 4 9 | fvmpt | ⊢ ( 𝑥  ∈  V  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  =  ( 𝐴 𝐹 𝑥 ) ) | 
						
							| 11 | 10 | elv | ⊢ ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  =  ( 𝐴 𝐹 𝑥 ) | 
						
							| 12 | 11 | a1i | ⊢ ( 𝑥  ∈  𝑦  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  =  ( 𝐴 𝐹 𝑥 ) ) | 
						
							| 13 | 12 | iuneq2i | ⊢ ∪  𝑥  ∈  𝑦 ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  =  ∪  𝑥  ∈  𝑦 ( 𝐴 𝐹 𝑥 ) | 
						
							| 14 | 1 7 13 | 3eqtr4g | ⊢ ( Lim  𝑦  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑦 )  =  ∪  𝑥  ∈  𝑦 ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 ) ) | 
						
							| 15 | 2 11 7 | 3sstr4g | ⊢ ( ( 𝑥  ∈  On  ∧  𝑦  ∈  On  ∧  𝑥  ⊆  𝑦 )  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  ⊆  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑦 ) ) | 
						
							| 16 | 14 15 | onfununi | ⊢ ( ( 𝑆  ∈  𝑇  ∧  𝑆  ⊆  On  ∧  𝑆  ≠  ∅ )  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ ∪  𝑆 )  =  ∪  𝑥  ∈  𝑆 ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 ) ) | 
						
							| 17 |  | uniexg | ⊢ ( 𝑆  ∈  𝑇  →  ∪  𝑆  ∈  V ) | 
						
							| 18 |  | oveq2 | ⊢ ( 𝑧  =  ∪  𝑆  →  ( 𝐴 𝐹 𝑧 )  =  ( 𝐴 𝐹 ∪  𝑆 ) ) | 
						
							| 19 |  | ovex | ⊢ ( 𝐴 𝐹 ∪  𝑆 )  ∈  V | 
						
							| 20 | 18 4 19 | fvmpt | ⊢ ( ∪  𝑆  ∈  V  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ ∪  𝑆 )  =  ( 𝐴 𝐹 ∪  𝑆 ) ) | 
						
							| 21 | 17 20 | syl | ⊢ ( 𝑆  ∈  𝑇  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ ∪  𝑆 )  =  ( 𝐴 𝐹 ∪  𝑆 ) ) | 
						
							| 22 | 21 | 3ad2ant1 | ⊢ ( ( 𝑆  ∈  𝑇  ∧  𝑆  ⊆  On  ∧  𝑆  ≠  ∅ )  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ ∪  𝑆 )  =  ( 𝐴 𝐹 ∪  𝑆 ) ) | 
						
							| 23 | 11 | a1i | ⊢ ( 𝑥  ∈  𝑆  →  ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  =  ( 𝐴 𝐹 𝑥 ) ) | 
						
							| 24 | 23 | iuneq2i | ⊢ ∪  𝑥  ∈  𝑆 ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  =  ∪  𝑥  ∈  𝑆 ( 𝐴 𝐹 𝑥 ) | 
						
							| 25 | 24 | a1i | ⊢ ( ( 𝑆  ∈  𝑇  ∧  𝑆  ⊆  On  ∧  𝑆  ≠  ∅ )  →  ∪  𝑥  ∈  𝑆 ( ( 𝑧  ∈  V  ↦  ( 𝐴 𝐹 𝑧 ) ) ‘ 𝑥 )  =  ∪  𝑥  ∈  𝑆 ( 𝐴 𝐹 𝑥 ) ) | 
						
							| 26 | 16 22 25 | 3eqtr3d | ⊢ ( ( 𝑆  ∈  𝑇  ∧  𝑆  ⊆  On  ∧  𝑆  ≠  ∅ )  →  ( 𝐴 𝐹 ∪  𝑆 )  =  ∪  𝑥  ∈  𝑆 ( 𝐴 𝐹 𝑥 ) ) |