| Step | Hyp | Ref | Expression | 
						
							| 1 |  | opprnzr.1 |  |-  O = ( oppR ` R ) | 
						
							| 2 | 1 | opprringb |  |-  ( R e. Ring <-> O e. Ring ) | 
						
							| 3 | 2 | anbi1i |  |-  ( ( R e. Ring /\ ( 1r ` R ) =/= ( 0g ` R ) ) <-> ( O e. Ring /\ ( 1r ` R ) =/= ( 0g ` R ) ) ) | 
						
							| 4 |  | eqid |  |-  ( 1r ` R ) = ( 1r ` R ) | 
						
							| 5 |  | eqid |  |-  ( 0g ` R ) = ( 0g ` R ) | 
						
							| 6 | 4 5 | isnzr |  |-  ( R e. NzRing <-> ( R e. Ring /\ ( 1r ` R ) =/= ( 0g ` R ) ) ) | 
						
							| 7 | 1 4 | oppr1 |  |-  ( 1r ` R ) = ( 1r ` O ) | 
						
							| 8 | 1 5 | oppr0 |  |-  ( 0g ` R ) = ( 0g ` O ) | 
						
							| 9 | 7 8 | isnzr |  |-  ( O e. NzRing <-> ( O e. Ring /\ ( 1r ` R ) =/= ( 0g ` R ) ) ) | 
						
							| 10 | 3 6 9 | 3bitr4i |  |-  ( R e. NzRing <-> O e. NzRing ) |