| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ttrclselem.1 | ⊢ 𝐹  =  rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) | 
						
							| 2 |  | nn0suc | ⊢ ( 𝑁  ∈  ω  →  ( 𝑁  =  ∅  ∨  ∃ 𝑛  ∈  ω 𝑁  =  suc  𝑛 ) ) | 
						
							| 3 | 1 | fveq1i | ⊢ ( 𝐹 ‘ 𝑁 )  =  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ 𝑁 ) | 
						
							| 4 |  | fveq2 | ⊢ ( 𝑁  =  ∅  →  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ 𝑁 )  =  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ ∅ ) ) | 
						
							| 5 | 3 4 | eqtrid | ⊢ ( 𝑁  =  ∅  →  ( 𝐹 ‘ 𝑁 )  =  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ ∅ ) ) | 
						
							| 6 |  | rdg0g | ⊢ ( Pred ( 𝑅 ,  𝐴 ,  𝑋 )  ∈  V  →  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ ∅ )  =  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) | 
						
							| 7 |  | predss | ⊢ Pred ( 𝑅 ,  𝐴 ,  𝑋 )  ⊆  𝐴 | 
						
							| 8 | 6 7 | eqsstrdi | ⊢ ( Pred ( 𝑅 ,  𝐴 ,  𝑋 )  ∈  V  →  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ ∅ )  ⊆  𝐴 ) | 
						
							| 9 |  | rdg0n | ⊢ ( ¬  Pred ( 𝑅 ,  𝐴 ,  𝑋 )  ∈  V  →  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ ∅ )  =  ∅ ) | 
						
							| 10 |  | 0ss | ⊢ ∅  ⊆  𝐴 | 
						
							| 11 | 9 10 | eqsstrdi | ⊢ ( ¬  Pred ( 𝑅 ,  𝐴 ,  𝑋 )  ∈  V  →  ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ ∅ )  ⊆  𝐴 ) | 
						
							| 12 | 8 11 | pm2.61i | ⊢ ( rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) ‘ ∅ )  ⊆  𝐴 | 
						
							| 13 | 5 12 | eqsstrdi | ⊢ ( 𝑁  =  ∅  →  ( 𝐹 ‘ 𝑁 )  ⊆  𝐴 ) | 
						
							| 14 |  | nnon | ⊢ ( 𝑛  ∈  ω  →  𝑛  ∈  On ) | 
						
							| 15 |  | nfcv | ⊢ Ⅎ 𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑋 ) | 
						
							| 16 |  | nfcv | ⊢ Ⅎ 𝑏 𝑛 | 
						
							| 17 |  | nfmpt1 | ⊢ Ⅎ 𝑏 ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) | 
						
							| 18 | 17 15 | nfrdg | ⊢ Ⅎ 𝑏 rec ( ( 𝑏  ∈  V  ↦  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 ) ) ,  Pred ( 𝑅 ,  𝐴 ,  𝑋 ) ) | 
						
							| 19 | 1 18 | nfcxfr | ⊢ Ⅎ 𝑏 𝐹 | 
						
							| 20 | 19 16 | nffv | ⊢ Ⅎ 𝑏 ( 𝐹 ‘ 𝑛 ) | 
						
							| 21 |  | nfcv | ⊢ Ⅎ 𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑡 ) | 
						
							| 22 | 20 21 | nfiun | ⊢ Ⅎ 𝑏 ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 ) | 
						
							| 23 |  | predeq3 | ⊢ ( 𝑤  =  𝑡  →  Pred ( 𝑅 ,  𝐴 ,  𝑤 )  =  Pred ( 𝑅 ,  𝐴 ,  𝑡 ) ) | 
						
							| 24 | 23 | cbviunv | ⊢ ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 )  =  ∪  𝑡  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑡 ) | 
						
							| 25 |  | iuneq1 | ⊢ ( 𝑏  =  ( 𝐹 ‘ 𝑛 )  →  ∪  𝑡  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑡 )  =  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 ) ) | 
						
							| 26 | 24 25 | eqtrid | ⊢ ( 𝑏  =  ( 𝐹 ‘ 𝑛 )  →  ∪  𝑤  ∈  𝑏 Pred ( 𝑅 ,  𝐴 ,  𝑤 )  =  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 ) ) | 
						
							| 27 | 15 16 22 1 26 | rdgsucmptf | ⊢ ( ( 𝑛  ∈  On  ∧  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ∈  V )  →  ( 𝐹 ‘ suc  𝑛 )  =  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 ) ) | 
						
							| 28 |  | iunss | ⊢ ( ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ⊆  𝐴  ↔  ∀ 𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ⊆  𝐴 ) | 
						
							| 29 |  | predss | ⊢ Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ⊆  𝐴 | 
						
							| 30 | 29 | a1i | ⊢ ( 𝑡  ∈  ( 𝐹 ‘ 𝑛 )  →  Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ⊆  𝐴 ) | 
						
							| 31 | 28 30 | mprgbir | ⊢ ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ⊆  𝐴 | 
						
							| 32 | 27 31 | eqsstrdi | ⊢ ( ( 𝑛  ∈  On  ∧  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ∈  V )  →  ( 𝐹 ‘ suc  𝑛 )  ⊆  𝐴 ) | 
						
							| 33 | 14 32 | sylan | ⊢ ( ( 𝑛  ∈  ω  ∧  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ∈  V )  →  ( 𝐹 ‘ suc  𝑛 )  ⊆  𝐴 ) | 
						
							| 34 | 15 16 22 1 26 | rdgsucmptnf | ⊢ ( ¬  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ∈  V  →  ( 𝐹 ‘ suc  𝑛 )  =  ∅ ) | 
						
							| 35 | 34 10 | eqsstrdi | ⊢ ( ¬  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ∈  V  →  ( 𝐹 ‘ suc  𝑛 )  ⊆  𝐴 ) | 
						
							| 36 | 35 | adantl | ⊢ ( ( 𝑛  ∈  ω  ∧  ¬  ∪  𝑡  ∈  ( 𝐹 ‘ 𝑛 ) Pred ( 𝑅 ,  𝐴 ,  𝑡 )  ∈  V )  →  ( 𝐹 ‘ suc  𝑛 )  ⊆  𝐴 ) | 
						
							| 37 | 33 36 | pm2.61dan | ⊢ ( 𝑛  ∈  ω  →  ( 𝐹 ‘ suc  𝑛 )  ⊆  𝐴 ) | 
						
							| 38 |  | fveq2 | ⊢ ( 𝑁  =  suc  𝑛  →  ( 𝐹 ‘ 𝑁 )  =  ( 𝐹 ‘ suc  𝑛 ) ) | 
						
							| 39 | 38 | sseq1d | ⊢ ( 𝑁  =  suc  𝑛  →  ( ( 𝐹 ‘ 𝑁 )  ⊆  𝐴  ↔  ( 𝐹 ‘ suc  𝑛 )  ⊆  𝐴 ) ) | 
						
							| 40 | 37 39 | syl5ibrcom | ⊢ ( 𝑛  ∈  ω  →  ( 𝑁  =  suc  𝑛  →  ( 𝐹 ‘ 𝑁 )  ⊆  𝐴 ) ) | 
						
							| 41 | 40 | rexlimiv | ⊢ ( ∃ 𝑛  ∈  ω 𝑁  =  suc  𝑛  →  ( 𝐹 ‘ 𝑁 )  ⊆  𝐴 ) | 
						
							| 42 | 13 41 | jaoi | ⊢ ( ( 𝑁  =  ∅  ∨  ∃ 𝑛  ∈  ω 𝑁  =  suc  𝑛 )  →  ( 𝐹 ‘ 𝑁 )  ⊆  𝐴 ) | 
						
							| 43 | 2 42 | syl | ⊢ ( 𝑁  ∈  ω  →  ( 𝐹 ‘ 𝑁 )  ⊆  𝐴 ) |