| Step | Hyp | Ref | Expression | 
						
							| 1 |  | rankr1ai | ⊢ ( 𝐴  ∈  ( 𝑅1 ‘ 𝐵 )  →  ( rank ‘ 𝐴 )  ∈  𝐵 ) | 
						
							| 2 |  | r1funlim | ⊢ ( Fun  𝑅1  ∧  Lim  dom  𝑅1 ) | 
						
							| 3 | 2 | simpri | ⊢ Lim  dom  𝑅1 | 
						
							| 4 |  | limord | ⊢ ( Lim  dom  𝑅1  →  Ord  dom  𝑅1 ) | 
						
							| 5 | 3 4 | ax-mp | ⊢ Ord  dom  𝑅1 | 
						
							| 6 |  | ordelord | ⊢ ( ( Ord  dom  𝑅1  ∧  𝐵  ∈  dom  𝑅1 )  →  Ord  𝐵 ) | 
						
							| 7 | 5 6 | mpan | ⊢ ( 𝐵  ∈  dom  𝑅1  →  Ord  𝐵 ) | 
						
							| 8 | 7 | adantl | ⊢ ( ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  ∧  𝐵  ∈  dom  𝑅1 )  →  Ord  𝐵 ) | 
						
							| 9 |  | ordsucss | ⊢ ( Ord  𝐵  →  ( ( rank ‘ 𝐴 )  ∈  𝐵  →  suc  ( rank ‘ 𝐴 )  ⊆  𝐵 ) ) | 
						
							| 10 | 8 9 | syl | ⊢ ( ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  ∧  𝐵  ∈  dom  𝑅1 )  →  ( ( rank ‘ 𝐴 )  ∈  𝐵  →  suc  ( rank ‘ 𝐴 )  ⊆  𝐵 ) ) | 
						
							| 11 |  | rankidb | ⊢ ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  →  𝐴  ∈  ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) ) ) | 
						
							| 12 |  | elfvdm | ⊢ ( 𝐴  ∈  ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) )  →  suc  ( rank ‘ 𝐴 )  ∈  dom  𝑅1 ) | 
						
							| 13 | 11 12 | syl | ⊢ ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  →  suc  ( rank ‘ 𝐴 )  ∈  dom  𝑅1 ) | 
						
							| 14 |  | r1ord3g | ⊢ ( ( suc  ( rank ‘ 𝐴 )  ∈  dom  𝑅1  ∧  𝐵  ∈  dom  𝑅1 )  →  ( suc  ( rank ‘ 𝐴 )  ⊆  𝐵  →  ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) )  ⊆  ( 𝑅1 ‘ 𝐵 ) ) ) | 
						
							| 15 | 13 14 | sylan | ⊢ ( ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  ∧  𝐵  ∈  dom  𝑅1 )  →  ( suc  ( rank ‘ 𝐴 )  ⊆  𝐵  →  ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) )  ⊆  ( 𝑅1 ‘ 𝐵 ) ) ) | 
						
							| 16 | 11 | adantr | ⊢ ( ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  ∧  𝐵  ∈  dom  𝑅1 )  →  𝐴  ∈  ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) ) ) | 
						
							| 17 |  | ssel | ⊢ ( ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) )  ⊆  ( 𝑅1 ‘ 𝐵 )  →  ( 𝐴  ∈  ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) )  →  𝐴  ∈  ( 𝑅1 ‘ 𝐵 ) ) ) | 
						
							| 18 | 16 17 | syl5com | ⊢ ( ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  ∧  𝐵  ∈  dom  𝑅1 )  →  ( ( 𝑅1 ‘ suc  ( rank ‘ 𝐴 ) )  ⊆  ( 𝑅1 ‘ 𝐵 )  →  𝐴  ∈  ( 𝑅1 ‘ 𝐵 ) ) ) | 
						
							| 19 | 10 15 18 | 3syld | ⊢ ( ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  ∧  𝐵  ∈  dom  𝑅1 )  →  ( ( rank ‘ 𝐴 )  ∈  𝐵  →  𝐴  ∈  ( 𝑅1 ‘ 𝐵 ) ) ) | 
						
							| 20 | 1 19 | impbid2 | ⊢ ( ( 𝐴  ∈  ∪  ( 𝑅1  “  On )  ∧  𝐵  ∈  dom  𝑅1 )  →  ( 𝐴  ∈  ( 𝑅1 ‘ 𝐵 )  ↔  ( rank ‘ 𝐴 )  ∈  𝐵 ) ) |