| Step | Hyp | Ref | Expression | 
						
							| 1 |  | r1funlim |  |-  ( Fun R1 /\ Lim dom R1 ) | 
						
							| 2 | 1 | simpri |  |-  Lim dom R1 | 
						
							| 3 |  | limsuc |  |-  ( Lim dom R1 -> ( B e. dom R1 <-> suc B e. dom R1 ) ) | 
						
							| 4 | 2 3 | ax-mp |  |-  ( B e. dom R1 <-> suc B e. dom R1 ) | 
						
							| 5 |  | rankr1ag |  |-  ( ( A e. U. ( R1 " On ) /\ suc B e. dom R1 ) -> ( A e. ( R1 ` suc B ) <-> ( rank ` A ) e. suc B ) ) | 
						
							| 6 | 4 5 | sylan2b |  |-  ( ( A e. U. ( R1 " On ) /\ B e. dom R1 ) -> ( A e. ( R1 ` suc B ) <-> ( rank ` A ) e. suc B ) ) | 
						
							| 7 |  | r1sucg |  |-  ( B e. dom R1 -> ( R1 ` suc B ) = ~P ( R1 ` B ) ) | 
						
							| 8 | 7 | adantl |  |-  ( ( A e. U. ( R1 " On ) /\ B e. dom R1 ) -> ( R1 ` suc B ) = ~P ( R1 ` B ) ) | 
						
							| 9 | 8 | eleq2d |  |-  ( ( A e. U. ( R1 " On ) /\ B e. dom R1 ) -> ( A e. ( R1 ` suc B ) <-> A e. ~P ( R1 ` B ) ) ) | 
						
							| 10 |  | fvex |  |-  ( R1 ` B ) e. _V | 
						
							| 11 | 10 | elpw2 |  |-  ( A e. ~P ( R1 ` B ) <-> A C_ ( R1 ` B ) ) | 
						
							| 12 | 9 11 | bitr2di |  |-  ( ( A e. U. ( R1 " On ) /\ B e. dom R1 ) -> ( A C_ ( R1 ` B ) <-> A e. ( R1 ` suc B ) ) ) | 
						
							| 13 |  | rankon |  |-  ( rank ` A ) e. On | 
						
							| 14 |  | limord |  |-  ( Lim dom R1 -> Ord dom R1 ) | 
						
							| 15 | 2 14 | ax-mp |  |-  Ord dom R1 | 
						
							| 16 |  | ordelon |  |-  ( ( Ord dom R1 /\ B e. dom R1 ) -> B e. On ) | 
						
							| 17 | 15 16 | mpan |  |-  ( B e. dom R1 -> B e. On ) | 
						
							| 18 | 17 | adantl |  |-  ( ( A e. U. ( R1 " On ) /\ B e. dom R1 ) -> B e. On ) | 
						
							| 19 |  | onsssuc |  |-  ( ( ( rank ` A ) e. On /\ B e. On ) -> ( ( rank ` A ) C_ B <-> ( rank ` A ) e. suc B ) ) | 
						
							| 20 | 13 18 19 | sylancr |  |-  ( ( A e. U. ( R1 " On ) /\ B e. dom R1 ) -> ( ( rank ` A ) C_ B <-> ( rank ` A ) e. suc B ) ) | 
						
							| 21 | 6 12 20 | 3bitr4d |  |-  ( ( A e. U. ( R1 " On ) /\ B e. dom R1 ) -> ( A C_ ( R1 ` B ) <-> ( rank ` A ) C_ B ) ) |