| Step | Hyp | Ref | Expression | 
						
							| 1 |  | xpsff1o.f |  |-  F = ( x e. A , y e. B |-> { <. (/) , x >. , <. 1o , y >. } ) | 
						
							| 2 |  | xpsfrnel2 |  |-  ( { <. (/) , x >. , <. 1o , y >. } e. X_ k e. 2o if ( k = (/) , A , B ) <-> ( x e. A /\ y e. B ) ) | 
						
							| 3 | 2 | biimpri |  |-  ( ( x e. A /\ y e. B ) -> { <. (/) , x >. , <. 1o , y >. } e. X_ k e. 2o if ( k = (/) , A , B ) ) | 
						
							| 4 | 3 | rgen2 |  |-  A. x e. A A. y e. B { <. (/) , x >. , <. 1o , y >. } e. X_ k e. 2o if ( k = (/) , A , B ) | 
						
							| 5 | 1 | fmpo |  |-  ( A. x e. A A. y e. B { <. (/) , x >. , <. 1o , y >. } e. X_ k e. 2o if ( k = (/) , A , B ) <-> F : ( A X. B ) --> X_ k e. 2o if ( k = (/) , A , B ) ) | 
						
							| 6 | 4 5 | mpbi |  |-  F : ( A X. B ) --> X_ k e. 2o if ( k = (/) , A , B ) | 
						
							| 7 |  | 1st2nd2 |  |-  ( z e. ( A X. B ) -> z = <. ( 1st ` z ) , ( 2nd ` z ) >. ) | 
						
							| 8 | 7 | fveq2d |  |-  ( z e. ( A X. B ) -> ( F ` z ) = ( F ` <. ( 1st ` z ) , ( 2nd ` z ) >. ) ) | 
						
							| 9 |  | df-ov |  |-  ( ( 1st ` z ) F ( 2nd ` z ) ) = ( F ` <. ( 1st ` z ) , ( 2nd ` z ) >. ) | 
						
							| 10 |  | xp1st |  |-  ( z e. ( A X. B ) -> ( 1st ` z ) e. A ) | 
						
							| 11 |  | xp2nd |  |-  ( z e. ( A X. B ) -> ( 2nd ` z ) e. B ) | 
						
							| 12 | 1 | xpsfval |  |-  ( ( ( 1st ` z ) e. A /\ ( 2nd ` z ) e. B ) -> ( ( 1st ` z ) F ( 2nd ` z ) ) = { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ) | 
						
							| 13 | 10 11 12 | syl2anc |  |-  ( z e. ( A X. B ) -> ( ( 1st ` z ) F ( 2nd ` z ) ) = { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ) | 
						
							| 14 | 9 13 | eqtr3id |  |-  ( z e. ( A X. B ) -> ( F ` <. ( 1st ` z ) , ( 2nd ` z ) >. ) = { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ) | 
						
							| 15 | 8 14 | eqtrd |  |-  ( z e. ( A X. B ) -> ( F ` z ) = { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ) | 
						
							| 16 |  | 1st2nd2 |  |-  ( w e. ( A X. B ) -> w = <. ( 1st ` w ) , ( 2nd ` w ) >. ) | 
						
							| 17 | 16 | fveq2d |  |-  ( w e. ( A X. B ) -> ( F ` w ) = ( F ` <. ( 1st ` w ) , ( 2nd ` w ) >. ) ) | 
						
							| 18 |  | df-ov |  |-  ( ( 1st ` w ) F ( 2nd ` w ) ) = ( F ` <. ( 1st ` w ) , ( 2nd ` w ) >. ) | 
						
							| 19 |  | xp1st |  |-  ( w e. ( A X. B ) -> ( 1st ` w ) e. A ) | 
						
							| 20 |  | xp2nd |  |-  ( w e. ( A X. B ) -> ( 2nd ` w ) e. B ) | 
						
							| 21 | 1 | xpsfval |  |-  ( ( ( 1st ` w ) e. A /\ ( 2nd ` w ) e. B ) -> ( ( 1st ` w ) F ( 2nd ` w ) ) = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ) | 
						
							| 22 | 19 20 21 | syl2anc |  |-  ( w e. ( A X. B ) -> ( ( 1st ` w ) F ( 2nd ` w ) ) = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ) | 
						
							| 23 | 18 22 | eqtr3id |  |-  ( w e. ( A X. B ) -> ( F ` <. ( 1st ` w ) , ( 2nd ` w ) >. ) = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ) | 
						
							| 24 | 17 23 | eqtrd |  |-  ( w e. ( A X. B ) -> ( F ` w ) = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ) | 
						
							| 25 | 15 24 | eqeqan12d |  |-  ( ( z e. ( A X. B ) /\ w e. ( A X. B ) ) -> ( ( F ` z ) = ( F ` w ) <-> { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ) ) | 
						
							| 26 |  | fveq1 |  |-  ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } -> ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ` (/) ) = ( { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ` (/) ) ) | 
						
							| 27 |  | fvex |  |-  ( 1st ` z ) e. _V | 
						
							| 28 |  | fvpr0o |  |-  ( ( 1st ` z ) e. _V -> ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ` (/) ) = ( 1st ` z ) ) | 
						
							| 29 | 27 28 | ax-mp |  |-  ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ` (/) ) = ( 1st ` z ) | 
						
							| 30 |  | fvex |  |-  ( 1st ` w ) e. _V | 
						
							| 31 |  | fvpr0o |  |-  ( ( 1st ` w ) e. _V -> ( { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ` (/) ) = ( 1st ` w ) ) | 
						
							| 32 | 30 31 | ax-mp |  |-  ( { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ` (/) ) = ( 1st ` w ) | 
						
							| 33 | 26 29 32 | 3eqtr3g |  |-  ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } -> ( 1st ` z ) = ( 1st ` w ) ) | 
						
							| 34 |  | fveq1 |  |-  ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } -> ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ` 1o ) = ( { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ` 1o ) ) | 
						
							| 35 |  | fvex |  |-  ( 2nd ` z ) e. _V | 
						
							| 36 |  | fvpr1o |  |-  ( ( 2nd ` z ) e. _V -> ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ` 1o ) = ( 2nd ` z ) ) | 
						
							| 37 | 35 36 | ax-mp |  |-  ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } ` 1o ) = ( 2nd ` z ) | 
						
							| 38 |  | fvex |  |-  ( 2nd ` w ) e. _V | 
						
							| 39 |  | fvpr1o |  |-  ( ( 2nd ` w ) e. _V -> ( { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ` 1o ) = ( 2nd ` w ) ) | 
						
							| 40 | 38 39 | ax-mp |  |-  ( { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } ` 1o ) = ( 2nd ` w ) | 
						
							| 41 | 34 37 40 | 3eqtr3g |  |-  ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } -> ( 2nd ` z ) = ( 2nd ` w ) ) | 
						
							| 42 | 33 41 | opeq12d |  |-  ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } -> <. ( 1st ` z ) , ( 2nd ` z ) >. = <. ( 1st ` w ) , ( 2nd ` w ) >. ) | 
						
							| 43 | 7 16 | eqeqan12d |  |-  ( ( z e. ( A X. B ) /\ w e. ( A X. B ) ) -> ( z = w <-> <. ( 1st ` z ) , ( 2nd ` z ) >. = <. ( 1st ` w ) , ( 2nd ` w ) >. ) ) | 
						
							| 44 | 42 43 | imbitrrid |  |-  ( ( z e. ( A X. B ) /\ w e. ( A X. B ) ) -> ( { <. (/) , ( 1st ` z ) >. , <. 1o , ( 2nd ` z ) >. } = { <. (/) , ( 1st ` w ) >. , <. 1o , ( 2nd ` w ) >. } -> z = w ) ) | 
						
							| 45 | 25 44 | sylbid |  |-  ( ( z e. ( A X. B ) /\ w e. ( A X. B ) ) -> ( ( F ` z ) = ( F ` w ) -> z = w ) ) | 
						
							| 46 | 45 | rgen2 |  |-  A. z e. ( A X. B ) A. w e. ( A X. B ) ( ( F ` z ) = ( F ` w ) -> z = w ) | 
						
							| 47 |  | dff13 |  |-  ( F : ( A X. B ) -1-1-> X_ k e. 2o if ( k = (/) , A , B ) <-> ( F : ( A X. B ) --> X_ k e. 2o if ( k = (/) , A , B ) /\ A. z e. ( A X. B ) A. w e. ( A X. B ) ( ( F ` z ) = ( F ` w ) -> z = w ) ) ) | 
						
							| 48 | 6 46 47 | mpbir2an |  |-  F : ( A X. B ) -1-1-> X_ k e. 2o if ( k = (/) , A , B ) | 
						
							| 49 |  | xpsfrnel |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) <-> ( z Fn 2o /\ ( z ` (/) ) e. A /\ ( z ` 1o ) e. B ) ) | 
						
							| 50 | 49 | simp2bi |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) -> ( z ` (/) ) e. A ) | 
						
							| 51 | 49 | simp3bi |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) -> ( z ` 1o ) e. B ) | 
						
							| 52 | 1 | xpsfval |  |-  ( ( ( z ` (/) ) e. A /\ ( z ` 1o ) e. B ) -> ( ( z ` (/) ) F ( z ` 1o ) ) = { <. (/) , ( z ` (/) ) >. , <. 1o , ( z ` 1o ) >. } ) | 
						
							| 53 | 50 51 52 | syl2anc |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) -> ( ( z ` (/) ) F ( z ` 1o ) ) = { <. (/) , ( z ` (/) ) >. , <. 1o , ( z ` 1o ) >. } ) | 
						
							| 54 |  | ixpfn |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) -> z Fn 2o ) | 
						
							| 55 |  | xpsfeq |  |-  ( z Fn 2o -> { <. (/) , ( z ` (/) ) >. , <. 1o , ( z ` 1o ) >. } = z ) | 
						
							| 56 | 54 55 | syl |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) -> { <. (/) , ( z ` (/) ) >. , <. 1o , ( z ` 1o ) >. } = z ) | 
						
							| 57 | 53 56 | eqtr2d |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) -> z = ( ( z ` (/) ) F ( z ` 1o ) ) ) | 
						
							| 58 |  | rspceov |  |-  ( ( ( z ` (/) ) e. A /\ ( z ` 1o ) e. B /\ z = ( ( z ` (/) ) F ( z ` 1o ) ) ) -> E. a e. A E. b e. B z = ( a F b ) ) | 
						
							| 59 | 50 51 57 58 | syl3anc |  |-  ( z e. X_ k e. 2o if ( k = (/) , A , B ) -> E. a e. A E. b e. B z = ( a F b ) ) | 
						
							| 60 | 59 | rgen |  |-  A. z e. X_ k e. 2o if ( k = (/) , A , B ) E. a e. A E. b e. B z = ( a F b ) | 
						
							| 61 |  | foov |  |-  ( F : ( A X. B ) -onto-> X_ k e. 2o if ( k = (/) , A , B ) <-> ( F : ( A X. B ) --> X_ k e. 2o if ( k = (/) , A , B ) /\ A. z e. X_ k e. 2o if ( k = (/) , A , B ) E. a e. A E. b e. B z = ( a F b ) ) ) | 
						
							| 62 | 6 60 61 | mpbir2an |  |-  F : ( A X. B ) -onto-> X_ k e. 2o if ( k = (/) , A , B ) | 
						
							| 63 |  | df-f1o |  |-  ( F : ( A X. B ) -1-1-onto-> X_ k e. 2o if ( k = (/) , A , B ) <-> ( F : ( A X. B ) -1-1-> X_ k e. 2o if ( k = (/) , A , B ) /\ F : ( A X. B ) -onto-> X_ k e. 2o if ( k = (/) , A , B ) ) ) | 
						
							| 64 | 48 62 63 | mpbir2an |  |-  F : ( A X. B ) -1-1-onto-> X_ k e. 2o if ( k = (/) , A , B ) |