| Step | Hyp | Ref | Expression | 
						
							| 1 |  | copsex4g.1 |  |-  ( ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) -> ( ph <-> ps ) ) | 
						
							| 2 |  | eqcom |  |-  ( <. A , B >. = <. x , y >. <-> <. x , y >. = <. A , B >. ) | 
						
							| 3 |  | vex |  |-  x e. _V | 
						
							| 4 |  | vex |  |-  y e. _V | 
						
							| 5 | 3 4 | opth |  |-  ( <. x , y >. = <. A , B >. <-> ( x = A /\ y = B ) ) | 
						
							| 6 | 2 5 | bitri |  |-  ( <. A , B >. = <. x , y >. <-> ( x = A /\ y = B ) ) | 
						
							| 7 |  | eqcom |  |-  ( <. C , D >. = <. z , w >. <-> <. z , w >. = <. C , D >. ) | 
						
							| 8 |  | vex |  |-  z e. _V | 
						
							| 9 |  | vex |  |-  w e. _V | 
						
							| 10 | 8 9 | opth |  |-  ( <. z , w >. = <. C , D >. <-> ( z = C /\ w = D ) ) | 
						
							| 11 | 7 10 | bitri |  |-  ( <. C , D >. = <. z , w >. <-> ( z = C /\ w = D ) ) | 
						
							| 12 | 6 11 | anbi12i |  |-  ( ( <. A , B >. = <. x , y >. /\ <. C , D >. = <. z , w >. ) <-> ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) ) | 
						
							| 13 | 12 | anbi1i |  |-  ( ( ( <. A , B >. = <. x , y >. /\ <. C , D >. = <. z , w >. ) /\ ph ) <-> ( ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) /\ ph ) ) | 
						
							| 14 | 13 | a1i |  |-  ( ( ( A e. R /\ B e. S ) /\ ( C e. R /\ D e. S ) ) -> ( ( ( <. A , B >. = <. x , y >. /\ <. C , D >. = <. z , w >. ) /\ ph ) <-> ( ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) /\ ph ) ) ) | 
						
							| 15 | 14 | 4exbidv |  |-  ( ( ( A e. R /\ B e. S ) /\ ( C e. R /\ D e. S ) ) -> ( E. x E. y E. z E. w ( ( <. A , B >. = <. x , y >. /\ <. C , D >. = <. z , w >. ) /\ ph ) <-> E. x E. y E. z E. w ( ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) /\ ph ) ) ) | 
						
							| 16 |  | id |  |-  ( ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) -> ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) ) | 
						
							| 17 | 16 1 | cgsex4g |  |-  ( ( ( A e. R /\ B e. S ) /\ ( C e. R /\ D e. S ) ) -> ( E. x E. y E. z E. w ( ( ( x = A /\ y = B ) /\ ( z = C /\ w = D ) ) /\ ph ) <-> ps ) ) | 
						
							| 18 | 15 17 | bitrd |  |-  ( ( ( A e. R /\ B e. S ) /\ ( C e. R /\ D e. S ) ) -> ( E. x E. y E. z E. w ( ( <. A , B >. = <. x , y >. /\ <. C , D >. = <. z , w >. ) /\ ph ) <-> ps ) ) |