| Step | Hyp | Ref | Expression | 
						
							| 1 |  | tngnm.t |  |-  T = ( G toNrmGrp N ) | 
						
							| 2 |  | tngnm.x |  |-  X = ( Base ` G ) | 
						
							| 3 |  | tngnm.a |  |-  A e. _V | 
						
							| 4 |  | simpr |  |-  ( ( G e. Grp /\ N : X --> A ) -> N : X --> A ) | 
						
							| 5 | 4 | feqmptd |  |-  ( ( G e. Grp /\ N : X --> A ) -> N = ( x e. X |-> ( N ` x ) ) ) | 
						
							| 6 |  | eqid |  |-  ( -g ` G ) = ( -g ` G ) | 
						
							| 7 | 2 6 | grpsubf |  |-  ( G e. Grp -> ( -g ` G ) : ( X X. X ) --> X ) | 
						
							| 8 | 7 | ad2antrr |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> ( -g ` G ) : ( X X. X ) --> X ) | 
						
							| 9 |  | simpr |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> x e. X ) | 
						
							| 10 |  | eqid |  |-  ( 0g ` G ) = ( 0g ` G ) | 
						
							| 11 | 2 10 | grpidcl |  |-  ( G e. Grp -> ( 0g ` G ) e. X ) | 
						
							| 12 | 11 | ad2antrr |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> ( 0g ` G ) e. X ) | 
						
							| 13 | 9 12 | opelxpd |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> <. x , ( 0g ` G ) >. e. ( X X. X ) ) | 
						
							| 14 |  | fvco3 |  |-  ( ( ( -g ` G ) : ( X X. X ) --> X /\ <. x , ( 0g ` G ) >. e. ( X X. X ) ) -> ( ( N o. ( -g ` G ) ) ` <. x , ( 0g ` G ) >. ) = ( N ` ( ( -g ` G ) ` <. x , ( 0g ` G ) >. ) ) ) | 
						
							| 15 | 8 13 14 | syl2anc |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> ( ( N o. ( -g ` G ) ) ` <. x , ( 0g ` G ) >. ) = ( N ` ( ( -g ` G ) ` <. x , ( 0g ` G ) >. ) ) ) | 
						
							| 16 |  | df-ov |  |-  ( x ( N o. ( -g ` G ) ) ( 0g ` G ) ) = ( ( N o. ( -g ` G ) ) ` <. x , ( 0g ` G ) >. ) | 
						
							| 17 |  | df-ov |  |-  ( x ( -g ` G ) ( 0g ` G ) ) = ( ( -g ` G ) ` <. x , ( 0g ` G ) >. ) | 
						
							| 18 | 17 | fveq2i |  |-  ( N ` ( x ( -g ` G ) ( 0g ` G ) ) ) = ( N ` ( ( -g ` G ) ` <. x , ( 0g ` G ) >. ) ) | 
						
							| 19 | 15 16 18 | 3eqtr4g |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> ( x ( N o. ( -g ` G ) ) ( 0g ` G ) ) = ( N ` ( x ( -g ` G ) ( 0g ` G ) ) ) ) | 
						
							| 20 | 2 10 6 | grpsubid1 |  |-  ( ( G e. Grp /\ x e. X ) -> ( x ( -g ` G ) ( 0g ` G ) ) = x ) | 
						
							| 21 | 20 | adantlr |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> ( x ( -g ` G ) ( 0g ` G ) ) = x ) | 
						
							| 22 | 21 | fveq2d |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> ( N ` ( x ( -g ` G ) ( 0g ` G ) ) ) = ( N ` x ) ) | 
						
							| 23 | 19 22 | eqtr2d |  |-  ( ( ( G e. Grp /\ N : X --> A ) /\ x e. X ) -> ( N ` x ) = ( x ( N o. ( -g ` G ) ) ( 0g ` G ) ) ) | 
						
							| 24 | 23 | mpteq2dva |  |-  ( ( G e. Grp /\ N : X --> A ) -> ( x e. X |-> ( N ` x ) ) = ( x e. X |-> ( x ( N o. ( -g ` G ) ) ( 0g ` G ) ) ) ) | 
						
							| 25 | 2 | fvexi |  |-  X e. _V | 
						
							| 26 |  | fex2 |  |-  ( ( N : X --> A /\ X e. _V /\ A e. _V ) -> N e. _V ) | 
						
							| 27 | 25 3 26 | mp3an23 |  |-  ( N : X --> A -> N e. _V ) | 
						
							| 28 | 27 | adantl |  |-  ( ( G e. Grp /\ N : X --> A ) -> N e. _V ) | 
						
							| 29 | 1 2 | tngbas |  |-  ( N e. _V -> X = ( Base ` T ) ) | 
						
							| 30 | 28 29 | syl |  |-  ( ( G e. Grp /\ N : X --> A ) -> X = ( Base ` T ) ) | 
						
							| 31 | 1 6 | tngds |  |-  ( N e. _V -> ( N o. ( -g ` G ) ) = ( dist ` T ) ) | 
						
							| 32 | 28 31 | syl |  |-  ( ( G e. Grp /\ N : X --> A ) -> ( N o. ( -g ` G ) ) = ( dist ` T ) ) | 
						
							| 33 |  | eqidd |  |-  ( ( G e. Grp /\ N : X --> A ) -> x = x ) | 
						
							| 34 | 1 10 | tng0 |  |-  ( N e. _V -> ( 0g ` G ) = ( 0g ` T ) ) | 
						
							| 35 | 28 34 | syl |  |-  ( ( G e. Grp /\ N : X --> A ) -> ( 0g ` G ) = ( 0g ` T ) ) | 
						
							| 36 | 32 33 35 | oveq123d |  |-  ( ( G e. Grp /\ N : X --> A ) -> ( x ( N o. ( -g ` G ) ) ( 0g ` G ) ) = ( x ( dist ` T ) ( 0g ` T ) ) ) | 
						
							| 37 | 30 36 | mpteq12dv |  |-  ( ( G e. Grp /\ N : X --> A ) -> ( x e. X |-> ( x ( N o. ( -g ` G ) ) ( 0g ` G ) ) ) = ( x e. ( Base ` T ) |-> ( x ( dist ` T ) ( 0g ` T ) ) ) ) | 
						
							| 38 |  | eqid |  |-  ( norm ` T ) = ( norm ` T ) | 
						
							| 39 |  | eqid |  |-  ( Base ` T ) = ( Base ` T ) | 
						
							| 40 |  | eqid |  |-  ( 0g ` T ) = ( 0g ` T ) | 
						
							| 41 |  | eqid |  |-  ( dist ` T ) = ( dist ` T ) | 
						
							| 42 | 38 39 40 41 | nmfval |  |-  ( norm ` T ) = ( x e. ( Base ` T ) |-> ( x ( dist ` T ) ( 0g ` T ) ) ) | 
						
							| 43 | 37 42 | eqtr4di |  |-  ( ( G e. Grp /\ N : X --> A ) -> ( x e. X |-> ( x ( N o. ( -g ` G ) ) ( 0g ` G ) ) ) = ( norm ` T ) ) | 
						
							| 44 | 5 24 43 | 3eqtrd |  |-  ( ( G e. Grp /\ N : X --> A ) -> N = ( norm ` T ) ) |