| Step | Hyp | Ref | Expression | 
						
							| 1 |  | coiun |  |-  ( `' ( 1st |` ( _V X. _V ) ) o. U_ x e. A ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) = U_ x e. A ( `' ( 1st |` ( _V X. _V ) ) o. ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) | 
						
							| 2 |  | inss1 |  |-  ( dom F i^i ran ( 1st |` ( _V X. _V ) ) ) C_ dom F | 
						
							| 3 |  | fndm |  |-  ( F Fn A -> dom F = A ) | 
						
							| 4 | 2 3 | sseqtrid |  |-  ( F Fn A -> ( dom F i^i ran ( 1st |` ( _V X. _V ) ) ) C_ A ) | 
						
							| 5 |  | dfco2a |  |-  ( ( dom F i^i ran ( 1st |` ( _V X. _V ) ) ) C_ A -> ( F o. ( 1st |` ( _V X. _V ) ) ) = U_ x e. A ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) | 
						
							| 6 | 4 5 | syl |  |-  ( F Fn A -> ( F o. ( 1st |` ( _V X. _V ) ) ) = U_ x e. A ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) | 
						
							| 7 | 6 | coeq2d |  |-  ( F Fn A -> ( `' ( 1st |` ( _V X. _V ) ) o. ( F o. ( 1st |` ( _V X. _V ) ) ) ) = ( `' ( 1st |` ( _V X. _V ) ) o. U_ x e. A ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) ) | 
						
							| 8 |  | inss1 |  |-  ( dom ( { ( F ` x ) } X. ( { x } X. _V ) ) i^i ran ( 1st |` ( _V X. _V ) ) ) C_ dom ( { ( F ` x ) } X. ( { x } X. _V ) ) | 
						
							| 9 |  | dmxpss |  |-  dom ( { ( F ` x ) } X. ( { x } X. _V ) ) C_ { ( F ` x ) } | 
						
							| 10 | 8 9 | sstri |  |-  ( dom ( { ( F ` x ) } X. ( { x } X. _V ) ) i^i ran ( 1st |` ( _V X. _V ) ) ) C_ { ( F ` x ) } | 
						
							| 11 |  | dfco2a |  |-  ( ( dom ( { ( F ` x ) } X. ( { x } X. _V ) ) i^i ran ( 1st |` ( _V X. _V ) ) ) C_ { ( F ` x ) } -> ( ( { ( F ` x ) } X. ( { x } X. _V ) ) o. ( 1st |` ( _V X. _V ) ) ) = U_ y e. { ( F ` x ) } ( ( `' ( 1st |` ( _V X. _V ) ) " { y } ) X. ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { y } ) ) ) | 
						
							| 12 | 10 11 | ax-mp |  |-  ( ( { ( F ` x ) } X. ( { x } X. _V ) ) o. ( 1st |` ( _V X. _V ) ) ) = U_ y e. { ( F ` x ) } ( ( `' ( 1st |` ( _V X. _V ) ) " { y } ) X. ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { y } ) ) | 
						
							| 13 |  | fvex |  |-  ( F ` x ) e. _V | 
						
							| 14 |  | fparlem1 |  |-  ( `' ( 1st |` ( _V X. _V ) ) " { y } ) = ( { y } X. _V ) | 
						
							| 15 |  | sneq |  |-  ( y = ( F ` x ) -> { y } = { ( F ` x ) } ) | 
						
							| 16 | 15 | xpeq1d |  |-  ( y = ( F ` x ) -> ( { y } X. _V ) = ( { ( F ` x ) } X. _V ) ) | 
						
							| 17 | 14 16 | eqtrid |  |-  ( y = ( F ` x ) -> ( `' ( 1st |` ( _V X. _V ) ) " { y } ) = ( { ( F ` x ) } X. _V ) ) | 
						
							| 18 | 15 | imaeq2d |  |-  ( y = ( F ` x ) -> ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { y } ) = ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { ( F ` x ) } ) ) | 
						
							| 19 |  | df-ima |  |-  ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { ( F ` x ) } ) = ran ( ( { ( F ` x ) } X. ( { x } X. _V ) ) |` { ( F ` x ) } ) | 
						
							| 20 |  | ssid |  |-  { ( F ` x ) } C_ { ( F ` x ) } | 
						
							| 21 |  | xpssres |  |-  ( { ( F ` x ) } C_ { ( F ` x ) } -> ( ( { ( F ` x ) } X. ( { x } X. _V ) ) |` { ( F ` x ) } ) = ( { ( F ` x ) } X. ( { x } X. _V ) ) ) | 
						
							| 22 | 20 21 | ax-mp |  |-  ( ( { ( F ` x ) } X. ( { x } X. _V ) ) |` { ( F ` x ) } ) = ( { ( F ` x ) } X. ( { x } X. _V ) ) | 
						
							| 23 | 22 | rneqi |  |-  ran ( ( { ( F ` x ) } X. ( { x } X. _V ) ) |` { ( F ` x ) } ) = ran ( { ( F ` x ) } X. ( { x } X. _V ) ) | 
						
							| 24 | 13 | snnz |  |-  { ( F ` x ) } =/= (/) | 
						
							| 25 |  | rnxp |  |-  ( { ( F ` x ) } =/= (/) -> ran ( { ( F ` x ) } X. ( { x } X. _V ) ) = ( { x } X. _V ) ) | 
						
							| 26 | 24 25 | ax-mp |  |-  ran ( { ( F ` x ) } X. ( { x } X. _V ) ) = ( { x } X. _V ) | 
						
							| 27 | 23 26 | eqtri |  |-  ran ( ( { ( F ` x ) } X. ( { x } X. _V ) ) |` { ( F ` x ) } ) = ( { x } X. _V ) | 
						
							| 28 | 19 27 | eqtri |  |-  ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { ( F ` x ) } ) = ( { x } X. _V ) | 
						
							| 29 | 18 28 | eqtrdi |  |-  ( y = ( F ` x ) -> ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { y } ) = ( { x } X. _V ) ) | 
						
							| 30 | 17 29 | xpeq12d |  |-  ( y = ( F ` x ) -> ( ( `' ( 1st |` ( _V X. _V ) ) " { y } ) X. ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { y } ) ) = ( ( { ( F ` x ) } X. _V ) X. ( { x } X. _V ) ) ) | 
						
							| 31 | 13 30 | iunxsn |  |-  U_ y e. { ( F ` x ) } ( ( `' ( 1st |` ( _V X. _V ) ) " { y } ) X. ( ( { ( F ` x ) } X. ( { x } X. _V ) ) " { y } ) ) = ( ( { ( F ` x ) } X. _V ) X. ( { x } X. _V ) ) | 
						
							| 32 | 12 31 | eqtri |  |-  ( ( { ( F ` x ) } X. ( { x } X. _V ) ) o. ( 1st |` ( _V X. _V ) ) ) = ( ( { ( F ` x ) } X. _V ) X. ( { x } X. _V ) ) | 
						
							| 33 | 32 | cnveqi |  |-  `' ( ( { ( F ` x ) } X. ( { x } X. _V ) ) o. ( 1st |` ( _V X. _V ) ) ) = `' ( ( { ( F ` x ) } X. _V ) X. ( { x } X. _V ) ) | 
						
							| 34 |  | cnvco |  |-  `' ( ( { ( F ` x ) } X. ( { x } X. _V ) ) o. ( 1st |` ( _V X. _V ) ) ) = ( `' ( 1st |` ( _V X. _V ) ) o. `' ( { ( F ` x ) } X. ( { x } X. _V ) ) ) | 
						
							| 35 |  | cnvxp |  |-  `' ( ( { ( F ` x ) } X. _V ) X. ( { x } X. _V ) ) = ( ( { x } X. _V ) X. ( { ( F ` x ) } X. _V ) ) | 
						
							| 36 | 33 34 35 | 3eqtr3i |  |-  ( `' ( 1st |` ( _V X. _V ) ) o. `' ( { ( F ` x ) } X. ( { x } X. _V ) ) ) = ( ( { x } X. _V ) X. ( { ( F ` x ) } X. _V ) ) | 
						
							| 37 |  | fparlem1 |  |-  ( `' ( 1st |` ( _V X. _V ) ) " { x } ) = ( { x } X. _V ) | 
						
							| 38 | 37 | xpeq2i |  |-  ( { ( F ` x ) } X. ( `' ( 1st |` ( _V X. _V ) ) " { x } ) ) = ( { ( F ` x ) } X. ( { x } X. _V ) ) | 
						
							| 39 |  | fnsnfv |  |-  ( ( F Fn A /\ x e. A ) -> { ( F ` x ) } = ( F " { x } ) ) | 
						
							| 40 | 39 | xpeq1d |  |-  ( ( F Fn A /\ x e. A ) -> ( { ( F ` x ) } X. ( `' ( 1st |` ( _V X. _V ) ) " { x } ) ) = ( ( F " { x } ) X. ( `' ( 1st |` ( _V X. _V ) ) " { x } ) ) ) | 
						
							| 41 | 38 40 | eqtr3id |  |-  ( ( F Fn A /\ x e. A ) -> ( { ( F ` x ) } X. ( { x } X. _V ) ) = ( ( F " { x } ) X. ( `' ( 1st |` ( _V X. _V ) ) " { x } ) ) ) | 
						
							| 42 | 41 | cnveqd |  |-  ( ( F Fn A /\ x e. A ) -> `' ( { ( F ` x ) } X. ( { x } X. _V ) ) = `' ( ( F " { x } ) X. ( `' ( 1st |` ( _V X. _V ) ) " { x } ) ) ) | 
						
							| 43 |  | cnvxp |  |-  `' ( ( F " { x } ) X. ( `' ( 1st |` ( _V X. _V ) ) " { x } ) ) = ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) | 
						
							| 44 | 42 43 | eqtrdi |  |-  ( ( F Fn A /\ x e. A ) -> `' ( { ( F ` x ) } X. ( { x } X. _V ) ) = ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) | 
						
							| 45 | 44 | coeq2d |  |-  ( ( F Fn A /\ x e. A ) -> ( `' ( 1st |` ( _V X. _V ) ) o. `' ( { ( F ` x ) } X. ( { x } X. _V ) ) ) = ( `' ( 1st |` ( _V X. _V ) ) o. ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) ) | 
						
							| 46 | 36 45 | eqtr3id |  |-  ( ( F Fn A /\ x e. A ) -> ( ( { x } X. _V ) X. ( { ( F ` x ) } X. _V ) ) = ( `' ( 1st |` ( _V X. _V ) ) o. ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) ) | 
						
							| 47 | 46 | iuneq2dv |  |-  ( F Fn A -> U_ x e. A ( ( { x } X. _V ) X. ( { ( F ` x ) } X. _V ) ) = U_ x e. A ( `' ( 1st |` ( _V X. _V ) ) o. ( ( `' ( 1st |` ( _V X. _V ) ) " { x } ) X. ( F " { x } ) ) ) ) | 
						
							| 48 | 1 7 47 | 3eqtr4a |  |-  ( F Fn A -> ( `' ( 1st |` ( _V X. _V ) ) o. ( F o. ( 1st |` ( _V X. _V ) ) ) ) = U_ x e. A ( ( { x } X. _V ) X. ( { ( F ` x ) } X. _V ) ) ) |