| Step | Hyp | Ref | Expression | 
						
							| 1 |  | eloprabi.1 |  |-  ( x = ( 1st ` ( 1st ` A ) ) -> ( ph <-> ps ) ) | 
						
							| 2 |  | eloprabi.2 |  |-  ( y = ( 2nd ` ( 1st ` A ) ) -> ( ps <-> ch ) ) | 
						
							| 3 |  | eloprabi.3 |  |-  ( z = ( 2nd ` A ) -> ( ch <-> th ) ) | 
						
							| 4 |  | eqeq1 |  |-  ( w = A -> ( w = <. <. x , y >. , z >. <-> A = <. <. x , y >. , z >. ) ) | 
						
							| 5 | 4 | anbi1d |  |-  ( w = A -> ( ( w = <. <. x , y >. , z >. /\ ph ) <-> ( A = <. <. x , y >. , z >. /\ ph ) ) ) | 
						
							| 6 | 5 | 3exbidv |  |-  ( w = A -> ( E. x E. y E. z ( w = <. <. x , y >. , z >. /\ ph ) <-> E. x E. y E. z ( A = <. <. x , y >. , z >. /\ ph ) ) ) | 
						
							| 7 |  | df-oprab |  |-  { <. <. x , y >. , z >. | ph } = { w | E. x E. y E. z ( w = <. <. x , y >. , z >. /\ ph ) } | 
						
							| 8 | 6 7 | elab2g |  |-  ( A e. { <. <. x , y >. , z >. | ph } -> ( A e. { <. <. x , y >. , z >. | ph } <-> E. x E. y E. z ( A = <. <. x , y >. , z >. /\ ph ) ) ) | 
						
							| 9 | 8 | ibi |  |-  ( A e. { <. <. x , y >. , z >. | ph } -> E. x E. y E. z ( A = <. <. x , y >. , z >. /\ ph ) ) | 
						
							| 10 |  | opex |  |-  <. x , y >. e. _V | 
						
							| 11 |  | vex |  |-  z e. _V | 
						
							| 12 | 10 11 | op1std |  |-  ( A = <. <. x , y >. , z >. -> ( 1st ` A ) = <. x , y >. ) | 
						
							| 13 | 12 | fveq2d |  |-  ( A = <. <. x , y >. , z >. -> ( 1st ` ( 1st ` A ) ) = ( 1st ` <. x , y >. ) ) | 
						
							| 14 |  | vex |  |-  x e. _V | 
						
							| 15 |  | vex |  |-  y e. _V | 
						
							| 16 | 14 15 | op1st |  |-  ( 1st ` <. x , y >. ) = x | 
						
							| 17 | 13 16 | eqtr2di |  |-  ( A = <. <. x , y >. , z >. -> x = ( 1st ` ( 1st ` A ) ) ) | 
						
							| 18 | 17 1 | syl |  |-  ( A = <. <. x , y >. , z >. -> ( ph <-> ps ) ) | 
						
							| 19 | 12 | fveq2d |  |-  ( A = <. <. x , y >. , z >. -> ( 2nd ` ( 1st ` A ) ) = ( 2nd ` <. x , y >. ) ) | 
						
							| 20 | 14 15 | op2nd |  |-  ( 2nd ` <. x , y >. ) = y | 
						
							| 21 | 19 20 | eqtr2di |  |-  ( A = <. <. x , y >. , z >. -> y = ( 2nd ` ( 1st ` A ) ) ) | 
						
							| 22 | 21 2 | syl |  |-  ( A = <. <. x , y >. , z >. -> ( ps <-> ch ) ) | 
						
							| 23 | 10 11 | op2ndd |  |-  ( A = <. <. x , y >. , z >. -> ( 2nd ` A ) = z ) | 
						
							| 24 | 23 | eqcomd |  |-  ( A = <. <. x , y >. , z >. -> z = ( 2nd ` A ) ) | 
						
							| 25 | 24 3 | syl |  |-  ( A = <. <. x , y >. , z >. -> ( ch <-> th ) ) | 
						
							| 26 | 18 22 25 | 3bitrd |  |-  ( A = <. <. x , y >. , z >. -> ( ph <-> th ) ) | 
						
							| 27 | 26 | biimpa |  |-  ( ( A = <. <. x , y >. , z >. /\ ph ) -> th ) | 
						
							| 28 | 27 | exlimiv |  |-  ( E. z ( A = <. <. x , y >. , z >. /\ ph ) -> th ) | 
						
							| 29 | 28 | exlimiv |  |-  ( E. y E. z ( A = <. <. x , y >. , z >. /\ ph ) -> th ) | 
						
							| 30 | 29 | exlimiv |  |-  ( E. x E. y E. z ( A = <. <. x , y >. , z >. /\ ph ) -> th ) | 
						
							| 31 | 9 30 | syl |  |-  ( A e. { <. <. x , y >. , z >. | ph } -> th ) |