| Step | Hyp | Ref | Expression | 
						
							| 1 |  | id |  |-  ( F : A -1-1-onto-> B -> F : A -1-1-onto-> B ) | 
						
							| 2 |  | dff1o3 |  |-  ( F : A -1-1-onto-> B <-> ( F : A -onto-> B /\ Fun `' F ) ) | 
						
							| 3 |  | vex |  |-  a e. _V | 
						
							| 4 | 3 | funimaex |  |-  ( Fun `' F -> ( `' F " a ) e. _V ) | 
						
							| 5 | 2 4 | simplbiim |  |-  ( F : A -1-1-onto-> B -> ( `' F " a ) e. _V ) | 
						
							| 6 |  | f1ofun |  |-  ( F : A -1-1-onto-> B -> Fun F ) | 
						
							| 7 |  | vex |  |-  b e. _V | 
						
							| 8 | 7 | funimaex |  |-  ( Fun F -> ( F " b ) e. _V ) | 
						
							| 9 | 6 8 | syl |  |-  ( F : A -1-1-onto-> B -> ( F " b ) e. _V ) | 
						
							| 10 | 1 5 9 | f1opw2 |  |-  ( F : A -1-1-onto-> B -> ( b e. ~P A |-> ( F " b ) ) : ~P A -1-1-onto-> ~P B ) |