| Step | Hyp | Ref | Expression | 
						
							| 1 |  | isdrngdOLD.b |  |-  ( ph -> B = ( Base ` R ) ) | 
						
							| 2 |  | isdrngdOLD.t |  |-  ( ph -> .x. = ( .r ` R ) ) | 
						
							| 3 |  | isdrngdOLD.z |  |-  ( ph -> .0. = ( 0g ` R ) ) | 
						
							| 4 |  | isdrngdOLD.u |  |-  ( ph -> .1. = ( 1r ` R ) ) | 
						
							| 5 |  | isdrngdOLD.r |  |-  ( ph -> R e. Ring ) | 
						
							| 6 |  | isdrngdOLD.n |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( y e. B /\ y =/= .0. ) ) -> ( x .x. y ) =/= .0. ) | 
						
							| 7 |  | isdrngdOLD.o |  |-  ( ph -> .1. =/= .0. ) | 
						
							| 8 |  | isdrngdOLD.i |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) ) -> I e. B ) | 
						
							| 9 |  | isdrngdOLD.j |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) ) -> I =/= .0. ) | 
						
							| 10 |  | isdrngrdOLD.k |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) ) -> ( x .x. I ) = .1. ) | 
						
							| 11 |  | eqid |  |-  ( oppR ` R ) = ( oppR ` R ) | 
						
							| 12 |  | eqid |  |-  ( Base ` R ) = ( Base ` R ) | 
						
							| 13 | 11 12 | opprbas |  |-  ( Base ` R ) = ( Base ` ( oppR ` R ) ) | 
						
							| 14 | 1 13 | eqtrdi |  |-  ( ph -> B = ( Base ` ( oppR ` R ) ) ) | 
						
							| 15 |  | eqidd |  |-  ( ph -> ( .r ` ( oppR ` R ) ) = ( .r ` ( oppR ` R ) ) ) | 
						
							| 16 |  | eqid |  |-  ( 0g ` R ) = ( 0g ` R ) | 
						
							| 17 | 11 16 | oppr0 |  |-  ( 0g ` R ) = ( 0g ` ( oppR ` R ) ) | 
						
							| 18 | 3 17 | eqtrdi |  |-  ( ph -> .0. = ( 0g ` ( oppR ` R ) ) ) | 
						
							| 19 |  | eqid |  |-  ( 1r ` R ) = ( 1r ` R ) | 
						
							| 20 | 11 19 | oppr1 |  |-  ( 1r ` R ) = ( 1r ` ( oppR ` R ) ) | 
						
							| 21 | 4 20 | eqtrdi |  |-  ( ph -> .1. = ( 1r ` ( oppR ` R ) ) ) | 
						
							| 22 | 11 | opprring |  |-  ( R e. Ring -> ( oppR ` R ) e. Ring ) | 
						
							| 23 | 5 22 | syl |  |-  ( ph -> ( oppR ` R ) e. Ring ) | 
						
							| 24 |  | eleq1w |  |-  ( y = x -> ( y e. B <-> x e. B ) ) | 
						
							| 25 |  | neeq1 |  |-  ( y = x -> ( y =/= .0. <-> x =/= .0. ) ) | 
						
							| 26 | 24 25 | anbi12d |  |-  ( y = x -> ( ( y e. B /\ y =/= .0. ) <-> ( x e. B /\ x =/= .0. ) ) ) | 
						
							| 27 | 26 | 3anbi2d |  |-  ( y = x -> ( ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) <-> ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) ) ) | 
						
							| 28 |  | oveq1 |  |-  ( y = x -> ( y ( .r ` ( oppR ` R ) ) z ) = ( x ( .r ` ( oppR ` R ) ) z ) ) | 
						
							| 29 | 28 | neeq1d |  |-  ( y = x -> ( ( y ( .r ` ( oppR ` R ) ) z ) =/= .0. <-> ( x ( .r ` ( oppR ` R ) ) z ) =/= .0. ) ) | 
						
							| 30 | 27 29 | imbi12d |  |-  ( y = x -> ( ( ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) -> ( y ( .r ` ( oppR ` R ) ) z ) =/= .0. ) <-> ( ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) -> ( x ( .r ` ( oppR ` R ) ) z ) =/= .0. ) ) ) | 
						
							| 31 |  | eleq1w |  |-  ( x = z -> ( x e. B <-> z e. B ) ) | 
						
							| 32 |  | neeq1 |  |-  ( x = z -> ( x =/= .0. <-> z =/= .0. ) ) | 
						
							| 33 | 31 32 | anbi12d |  |-  ( x = z -> ( ( x e. B /\ x =/= .0. ) <-> ( z e. B /\ z =/= .0. ) ) ) | 
						
							| 34 | 33 | 3anbi3d |  |-  ( x = z -> ( ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( x e. B /\ x =/= .0. ) ) <-> ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) ) ) | 
						
							| 35 |  | oveq2 |  |-  ( x = z -> ( y ( .r ` ( oppR ` R ) ) x ) = ( y ( .r ` ( oppR ` R ) ) z ) ) | 
						
							| 36 | 35 | neeq1d |  |-  ( x = z -> ( ( y ( .r ` ( oppR ` R ) ) x ) =/= .0. <-> ( y ( .r ` ( oppR ` R ) ) z ) =/= .0. ) ) | 
						
							| 37 | 34 36 | imbi12d |  |-  ( x = z -> ( ( ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( x e. B /\ x =/= .0. ) ) -> ( y ( .r ` ( oppR ` R ) ) x ) =/= .0. ) <-> ( ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) -> ( y ( .r ` ( oppR ` R ) ) z ) =/= .0. ) ) ) | 
						
							| 38 | 2 | 3ad2ant1 |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( y e. B /\ y =/= .0. ) ) -> .x. = ( .r ` R ) ) | 
						
							| 39 | 38 | oveqd |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( y e. B /\ y =/= .0. ) ) -> ( x .x. y ) = ( x ( .r ` R ) y ) ) | 
						
							| 40 |  | eqid |  |-  ( .r ` R ) = ( .r ` R ) | 
						
							| 41 |  | eqid |  |-  ( .r ` ( oppR ` R ) ) = ( .r ` ( oppR ` R ) ) | 
						
							| 42 | 12 40 11 41 | opprmul |  |-  ( y ( .r ` ( oppR ` R ) ) x ) = ( x ( .r ` R ) y ) | 
						
							| 43 | 39 42 | eqtr4di |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( y e. B /\ y =/= .0. ) ) -> ( x .x. y ) = ( y ( .r ` ( oppR ` R ) ) x ) ) | 
						
							| 44 | 43 6 | eqnetrrd |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( y e. B /\ y =/= .0. ) ) -> ( y ( .r ` ( oppR ` R ) ) x ) =/= .0. ) | 
						
							| 45 | 44 | 3com23 |  |-  ( ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( x e. B /\ x =/= .0. ) ) -> ( y ( .r ` ( oppR ` R ) ) x ) =/= .0. ) | 
						
							| 46 | 37 45 | chvarvv |  |-  ( ( ph /\ ( y e. B /\ y =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) -> ( y ( .r ` ( oppR ` R ) ) z ) =/= .0. ) | 
						
							| 47 | 30 46 | chvarvv |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) /\ ( z e. B /\ z =/= .0. ) ) -> ( x ( .r ` ( oppR ` R ) ) z ) =/= .0. ) | 
						
							| 48 | 12 40 11 41 | opprmul |  |-  ( I ( .r ` ( oppR ` R ) ) x ) = ( x ( .r ` R ) I ) | 
						
							| 49 | 2 | adantr |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) ) -> .x. = ( .r ` R ) ) | 
						
							| 50 | 49 | oveqd |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) ) -> ( x .x. I ) = ( x ( .r ` R ) I ) ) | 
						
							| 51 | 50 10 | eqtr3d |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) ) -> ( x ( .r ` R ) I ) = .1. ) | 
						
							| 52 | 48 51 | eqtrid |  |-  ( ( ph /\ ( x e. B /\ x =/= .0. ) ) -> ( I ( .r ` ( oppR ` R ) ) x ) = .1. ) | 
						
							| 53 | 14 15 18 21 23 47 7 8 9 52 | isdrngdOLD |  |-  ( ph -> ( oppR ` R ) e. DivRing ) | 
						
							| 54 | 11 | opprdrng |  |-  ( R e. DivRing <-> ( oppR ` R ) e. DivRing ) | 
						
							| 55 | 53 54 | sylibr |  |-  ( ph -> R e. DivRing ) |