| Step | Hyp | Ref | Expression | 
						
							| 1 |  | n0i | ⊢ ( 𝑓  ∈  X 𝑥  ∈  𝐴 𝐵  →  ¬  X 𝑥  ∈  𝐴 𝐵  =  ∅ ) | 
						
							| 2 |  | ixpprc | ⊢ ( ¬  𝐴  ∈  V  →  X 𝑥  ∈  𝐴 𝐵  =  ∅ ) | 
						
							| 3 | 1 2 | nsyl2 | ⊢ ( 𝑓  ∈  X 𝑥  ∈  𝐴 𝐵  →  𝐴  ∈  V ) | 
						
							| 4 |  | id | ⊢ ( ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉  →  ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉 ) | 
						
							| 5 |  | iunexg | ⊢ ( ( 𝐴  ∈  V  ∧  ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉 )  →  ∪  𝑥  ∈  𝐴 𝐵  ∈  V ) | 
						
							| 6 | 3 4 5 | syl2anr | ⊢ ( ( ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉  ∧  𝑓  ∈  X 𝑥  ∈  𝐴 𝐵 )  →  ∪  𝑥  ∈  𝐴 𝐵  ∈  V ) | 
						
							| 7 |  | ixpssmap2g | ⊢ ( ∪  𝑥  ∈  𝐴 𝐵  ∈  V  →  X 𝑥  ∈  𝐴 𝐵  ⊆  ( ∪  𝑥  ∈  𝐴 𝐵  ↑m  𝐴 ) ) | 
						
							| 8 | 6 7 | syl | ⊢ ( ( ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉  ∧  𝑓  ∈  X 𝑥  ∈  𝐴 𝐵 )  →  X 𝑥  ∈  𝐴 𝐵  ⊆  ( ∪  𝑥  ∈  𝐴 𝐵  ↑m  𝐴 ) ) | 
						
							| 9 |  | simpr | ⊢ ( ( ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉  ∧  𝑓  ∈  X 𝑥  ∈  𝐴 𝐵 )  →  𝑓  ∈  X 𝑥  ∈  𝐴 𝐵 ) | 
						
							| 10 | 8 9 | sseldd | ⊢ ( ( ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉  ∧  𝑓  ∈  X 𝑥  ∈  𝐴 𝐵 )  →  𝑓  ∈  ( ∪  𝑥  ∈  𝐴 𝐵  ↑m  𝐴 ) ) | 
						
							| 11 | 10 | ex | ⊢ ( ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉  →  ( 𝑓  ∈  X 𝑥  ∈  𝐴 𝐵  →  𝑓  ∈  ( ∪  𝑥  ∈  𝐴 𝐵  ↑m  𝐴 ) ) ) | 
						
							| 12 | 11 | ssrdv | ⊢ ( ∀ 𝑥  ∈  𝐴 𝐵  ∈  𝑉  →  X 𝑥  ∈  𝐴 𝐵  ⊆  ( ∪  𝑥  ∈  𝐴 𝐵  ↑m  𝐴 ) ) |