| Step | Hyp | Ref | Expression | 
						
							| 1 |  | oppggic.o |  |-  O = ( oppG ` G ) | 
						
							| 2 |  | oppgcntz.z |  |-  Z = ( Cntz ` G ) | 
						
							| 3 |  | eqcom |  |-  ( ( x ( +g ` G ) y ) = ( y ( +g ` G ) x ) <-> ( y ( +g ` G ) x ) = ( x ( +g ` G ) y ) ) | 
						
							| 4 |  | eqid |  |-  ( +g ` G ) = ( +g ` G ) | 
						
							| 5 |  | eqid |  |-  ( +g ` O ) = ( +g ` O ) | 
						
							| 6 | 4 1 5 | oppgplus |  |-  ( x ( +g ` O ) y ) = ( y ( +g ` G ) x ) | 
						
							| 7 | 4 1 5 | oppgplus |  |-  ( y ( +g ` O ) x ) = ( x ( +g ` G ) y ) | 
						
							| 8 | 6 7 | eqeq12i |  |-  ( ( x ( +g ` O ) y ) = ( y ( +g ` O ) x ) <-> ( y ( +g ` G ) x ) = ( x ( +g ` G ) y ) ) | 
						
							| 9 | 3 8 | bitr4i |  |-  ( ( x ( +g ` G ) y ) = ( y ( +g ` G ) x ) <-> ( x ( +g ` O ) y ) = ( y ( +g ` O ) x ) ) | 
						
							| 10 | 9 | ralbii |  |-  ( A. y e. A ( x ( +g ` G ) y ) = ( y ( +g ` G ) x ) <-> A. y e. A ( x ( +g ` O ) y ) = ( y ( +g ` O ) x ) ) | 
						
							| 11 | 10 | anbi2i |  |-  ( ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` G ) y ) = ( y ( +g ` G ) x ) ) <-> ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` O ) y ) = ( y ( +g ` O ) x ) ) ) | 
						
							| 12 | 11 | anbi2i |  |-  ( ( A C_ ( Base ` G ) /\ ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` G ) y ) = ( y ( +g ` G ) x ) ) ) <-> ( A C_ ( Base ` G ) /\ ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` O ) y ) = ( y ( +g ` O ) x ) ) ) ) | 
						
							| 13 |  | eqid |  |-  ( Base ` G ) = ( Base ` G ) | 
						
							| 14 | 13 2 | cntzrcl |  |-  ( x e. ( Z ` A ) -> ( G e. _V /\ A C_ ( Base ` G ) ) ) | 
						
							| 15 | 14 | simprd |  |-  ( x e. ( Z ` A ) -> A C_ ( Base ` G ) ) | 
						
							| 16 | 13 4 2 | elcntz |  |-  ( A C_ ( Base ` G ) -> ( x e. ( Z ` A ) <-> ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` G ) y ) = ( y ( +g ` G ) x ) ) ) ) | 
						
							| 17 | 15 16 | biadanii |  |-  ( x e. ( Z ` A ) <-> ( A C_ ( Base ` G ) /\ ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` G ) y ) = ( y ( +g ` G ) x ) ) ) ) | 
						
							| 18 | 1 13 | oppgbas |  |-  ( Base ` G ) = ( Base ` O ) | 
						
							| 19 |  | eqid |  |-  ( Cntz ` O ) = ( Cntz ` O ) | 
						
							| 20 | 18 19 | cntzrcl |  |-  ( x e. ( ( Cntz ` O ) ` A ) -> ( O e. _V /\ A C_ ( Base ` G ) ) ) | 
						
							| 21 | 20 | simprd |  |-  ( x e. ( ( Cntz ` O ) ` A ) -> A C_ ( Base ` G ) ) | 
						
							| 22 | 18 5 19 | elcntz |  |-  ( A C_ ( Base ` G ) -> ( x e. ( ( Cntz ` O ) ` A ) <-> ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` O ) y ) = ( y ( +g ` O ) x ) ) ) ) | 
						
							| 23 | 21 22 | biadanii |  |-  ( x e. ( ( Cntz ` O ) ` A ) <-> ( A C_ ( Base ` G ) /\ ( x e. ( Base ` G ) /\ A. y e. A ( x ( +g ` O ) y ) = ( y ( +g ` O ) x ) ) ) ) | 
						
							| 24 | 12 17 23 | 3bitr4i |  |-  ( x e. ( Z ` A ) <-> x e. ( ( Cntz ` O ) ` A ) ) | 
						
							| 25 | 24 | eqriv |  |-  ( Z ` A ) = ( ( Cntz ` O ) ` A ) |