| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							bnj1121.1 | 
							⊢ ( 𝜃  ↔  ( 𝑅  FrSe  𝐴  ∧  𝑋  ∈  𝐴 ) )  | 
						
						
							| 2 | 
							
								
							 | 
							bnj1121.2 | 
							⊢ ( 𝜏  ↔  ( 𝐵  ∈  V  ∧   TrFo ( 𝐵 ,  𝐴 ,  𝑅 )  ∧   pred ( 𝑋 ,  𝐴 ,  𝑅 )  ⊆  𝐵 ) )  | 
						
						
							| 3 | 
							
								
							 | 
							bnj1121.3 | 
							⊢ ( 𝜒  ↔  ( 𝑛  ∈  𝐷  ∧  𝑓  Fn  𝑛  ∧  𝜑  ∧  𝜓 ) )  | 
						
						
							| 4 | 
							
								
							 | 
							bnj1121.4 | 
							⊢ ( 𝜁  ↔  ( 𝑖  ∈  𝑛  ∧  𝑧  ∈  ( 𝑓 ‘ 𝑖 ) ) )  | 
						
						
							| 5 | 
							
								
							 | 
							bnj1121.5 | 
							⊢ ( 𝜂  ↔  ( ( 𝑓  ∈  𝐾  ∧  𝑖  ∈  dom  𝑓 )  →  ( 𝑓 ‘ 𝑖 )  ⊆  𝐵 ) )  | 
						
						
							| 6 | 
							
								
							 | 
							bnj1121.6 | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  ∀ 𝑖  ∈  𝑛 𝜂 )  | 
						
						
							| 7 | 
							
								
							 | 
							bnj1121.7 | 
							⊢ 𝐾  =  { 𝑓  ∣  ∃ 𝑛  ∈  𝐷 ( 𝑓  Fn  𝑛  ∧  𝜑  ∧  𝜓 ) }  | 
						
						
							| 8 | 
							
								
							 | 
							19.8a | 
							⊢ ( 𝜒  →  ∃ 𝑛 𝜒 )  | 
						
						
							| 9 | 
							
								8
							 | 
							bnj707 | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  ∃ 𝑛 𝜒 )  | 
						
						
							| 10 | 
							
								3 7
							 | 
							bnj1083 | 
							⊢ ( 𝑓  ∈  𝐾  ↔  ∃ 𝑛 𝜒 )  | 
						
						
							| 11 | 
							
								9 10
							 | 
							sylibr | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  𝑓  ∈  𝐾 )  | 
						
						
							| 12 | 
							
								4
							 | 
							simplbi | 
							⊢ ( 𝜁  →  𝑖  ∈  𝑛 )  | 
						
						
							| 13 | 
							
								12
							 | 
							bnj708 | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  𝑖  ∈  𝑛 )  | 
						
						
							| 14 | 
							
								3
							 | 
							bnj1235 | 
							⊢ ( 𝜒  →  𝑓  Fn  𝑛 )  | 
						
						
							| 15 | 
							
								14
							 | 
							bnj707 | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  𝑓  Fn  𝑛 )  | 
						
						
							| 16 | 
							
								15
							 | 
							fndmd | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  dom  𝑓  =  𝑛 )  | 
						
						
							| 17 | 
							
								13 16
							 | 
							eleqtrrd | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  𝑖  ∈  dom  𝑓 )  | 
						
						
							| 18 | 
							
								6 13
							 | 
							bnj1294 | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  𝜂 )  | 
						
						
							| 19 | 
							
								18 5
							 | 
							sylib | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  ( ( 𝑓  ∈  𝐾  ∧  𝑖  ∈  dom  𝑓 )  →  ( 𝑓 ‘ 𝑖 )  ⊆  𝐵 ) )  | 
						
						
							| 20 | 
							
								11 17 19
							 | 
							mp2and | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  ( 𝑓 ‘ 𝑖 )  ⊆  𝐵 )  | 
						
						
							| 21 | 
							
								4
							 | 
							simprbi | 
							⊢ ( 𝜁  →  𝑧  ∈  ( 𝑓 ‘ 𝑖 ) )  | 
						
						
							| 22 | 
							
								21
							 | 
							bnj708 | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  𝑧  ∈  ( 𝑓 ‘ 𝑖 ) )  | 
						
						
							| 23 | 
							
								20 22
							 | 
							sseldd | 
							⊢ ( ( 𝜃  ∧  𝜏  ∧  𝜒  ∧  𝜁 )  →  𝑧  ∈  𝐵 )  |