| Step | Hyp | Ref | Expression | 
						
							| 1 |  | id |  |-  ( H Isom R , S ( A , B ) -> H Isom R , S ( A , B ) ) | 
						
							| 2 |  | isof1o |  |-  ( H Isom R , S ( A , B ) -> H : A -1-1-onto-> B ) | 
						
							| 3 |  | f1ofun |  |-  ( H : A -1-1-onto-> B -> Fun H ) | 
						
							| 4 |  | vex |  |-  x e. _V | 
						
							| 5 | 4 | funimaex |  |-  ( Fun H -> ( H " x ) e. _V ) | 
						
							| 6 | 2 3 5 | 3syl |  |-  ( H Isom R , S ( A , B ) -> ( H " x ) e. _V ) | 
						
							| 7 | 1 6 | isoselem |  |-  ( H Isom R , S ( A , B ) -> ( R Se A -> S Se B ) ) | 
						
							| 8 |  | isocnv |  |-  ( H Isom R , S ( A , B ) -> `' H Isom S , R ( B , A ) ) | 
						
							| 9 |  | isof1o |  |-  ( `' H Isom S , R ( B , A ) -> `' H : B -1-1-onto-> A ) | 
						
							| 10 |  | f1ofun |  |-  ( `' H : B -1-1-onto-> A -> Fun `' H ) | 
						
							| 11 | 4 | funimaex |  |-  ( Fun `' H -> ( `' H " x ) e. _V ) | 
						
							| 12 | 8 9 10 11 | 4syl |  |-  ( H Isom R , S ( A , B ) -> ( `' H " x ) e. _V ) | 
						
							| 13 | 8 12 | isoselem |  |-  ( H Isom R , S ( A , B ) -> ( S Se B -> R Se A ) ) | 
						
							| 14 | 7 13 | impbid |  |-  ( H Isom R , S ( A , B ) -> ( R Se A <-> S Se B ) ) |