| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							dff1o4 | 
							 |-  ( F : (/) -1-1-onto-> A <-> ( F Fn (/) /\ `' F Fn A ) )  | 
						
						
							| 2 | 
							
								
							 | 
							fn0 | 
							 |-  ( F Fn (/) <-> F = (/) )  | 
						
						
							| 3 | 
							
								2
							 | 
							biimpi | 
							 |-  ( F Fn (/) -> F = (/) )  | 
						
						
							| 4 | 
							
								3
							 | 
							adantr | 
							 |-  ( ( F Fn (/) /\ `' F Fn A ) -> F = (/) )  | 
						
						
							| 5 | 
							
								
							 | 
							cnveq | 
							 |-  ( F = (/) -> `' F = `' (/) )  | 
						
						
							| 6 | 
							
								
							 | 
							cnv0 | 
							 |-  `' (/) = (/)  | 
						
						
							| 7 | 
							
								5 6
							 | 
							eqtrdi | 
							 |-  ( F = (/) -> `' F = (/) )  | 
						
						
							| 8 | 
							
								2 7
							 | 
							sylbi | 
							 |-  ( F Fn (/) -> `' F = (/) )  | 
						
						
							| 9 | 
							
								8
							 | 
							fneq1d | 
							 |-  ( F Fn (/) -> ( `' F Fn A <-> (/) Fn A ) )  | 
						
						
							| 10 | 
							
								9
							 | 
							biimpa | 
							 |-  ( ( F Fn (/) /\ `' F Fn A ) -> (/) Fn A )  | 
						
						
							| 11 | 
							
								10
							 | 
							fndmd | 
							 |-  ( ( F Fn (/) /\ `' F Fn A ) -> dom (/) = A )  | 
						
						
							| 12 | 
							
								
							 | 
							dm0 | 
							 |-  dom (/) = (/)  | 
						
						
							| 13 | 
							
								11 12
							 | 
							eqtr3di | 
							 |-  ( ( F Fn (/) /\ `' F Fn A ) -> A = (/) )  | 
						
						
							| 14 | 
							
								4 13
							 | 
							jca | 
							 |-  ( ( F Fn (/) /\ `' F Fn A ) -> ( F = (/) /\ A = (/) ) )  | 
						
						
							| 15 | 
							
								2
							 | 
							biimpri | 
							 |-  ( F = (/) -> F Fn (/) )  | 
						
						
							| 16 | 
							
								15
							 | 
							adantr | 
							 |-  ( ( F = (/) /\ A = (/) ) -> F Fn (/) )  | 
						
						
							| 17 | 
							
								
							 | 
							eqid | 
							 |-  (/) = (/)  | 
						
						
							| 18 | 
							
								
							 | 
							fn0 | 
							 |-  ( (/) Fn (/) <-> (/) = (/) )  | 
						
						
							| 19 | 
							
								17 18
							 | 
							mpbir | 
							 |-  (/) Fn (/)  | 
						
						
							| 20 | 
							
								7
							 | 
							fneq1d | 
							 |-  ( F = (/) -> ( `' F Fn A <-> (/) Fn A ) )  | 
						
						
							| 21 | 
							
								
							 | 
							fneq2 | 
							 |-  ( A = (/) -> ( (/) Fn A <-> (/) Fn (/) ) )  | 
						
						
							| 22 | 
							
								20 21
							 | 
							sylan9bb | 
							 |-  ( ( F = (/) /\ A = (/) ) -> ( `' F Fn A <-> (/) Fn (/) ) )  | 
						
						
							| 23 | 
							
								19 22
							 | 
							mpbiri | 
							 |-  ( ( F = (/) /\ A = (/) ) -> `' F Fn A )  | 
						
						
							| 24 | 
							
								16 23
							 | 
							jca | 
							 |-  ( ( F = (/) /\ A = (/) ) -> ( F Fn (/) /\ `' F Fn A ) )  | 
						
						
							| 25 | 
							
								14 24
							 | 
							impbii | 
							 |-  ( ( F Fn (/) /\ `' F Fn A ) <-> ( F = (/) /\ A = (/) ) )  | 
						
						
							| 26 | 
							
								1 25
							 | 
							bitri | 
							 |-  ( F : (/) -1-1-onto-> A <-> ( F = (/) /\ A = (/) ) )  |