| Step | Hyp | Ref | Expression | 
						
							| 1 |  | tngbas.t | ⊢ 𝑇  =  ( 𝐺  toNrmGrp  𝑁 ) | 
						
							| 2 |  | tnglem.e | ⊢ 𝐸  =  Slot  ( 𝐸 ‘ ndx ) | 
						
							| 3 |  | tnglem.t | ⊢ ( 𝐸 ‘ ndx )  ≠  ( TopSet ‘ ndx ) | 
						
							| 4 |  | tnglem.d | ⊢ ( 𝐸 ‘ ndx )  ≠  ( dist ‘ ndx ) | 
						
							| 5 | 2 4 | setsnid | ⊢ ( 𝐸 ‘ 𝐺 )  =  ( 𝐸 ‘ ( 𝐺  sSet  〈 ( dist ‘ ndx ) ,  ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) 〉 ) ) | 
						
							| 6 | 2 3 | setsnid | ⊢ ( 𝐸 ‘ ( 𝐺  sSet  〈 ( dist ‘ ndx ) ,  ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) 〉 ) )  =  ( 𝐸 ‘ ( ( 𝐺  sSet  〈 ( dist ‘ ndx ) ,  ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) 〉 )  sSet  〈 ( TopSet ‘ ndx ) ,  ( MetOpen ‘ ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) ) 〉 ) ) | 
						
							| 7 | 5 6 | eqtri | ⊢ ( 𝐸 ‘ 𝐺 )  =  ( 𝐸 ‘ ( ( 𝐺  sSet  〈 ( dist ‘ ndx ) ,  ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) 〉 )  sSet  〈 ( TopSet ‘ ndx ) ,  ( MetOpen ‘ ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) ) 〉 ) ) | 
						
							| 8 |  | eqid | ⊢ ( -g ‘ 𝐺 )  =  ( -g ‘ 𝐺 ) | 
						
							| 9 |  | eqid | ⊢ ( 𝑁  ∘  ( -g ‘ 𝐺 ) )  =  ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) | 
						
							| 10 |  | eqid | ⊢ ( MetOpen ‘ ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) )  =  ( MetOpen ‘ ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) ) | 
						
							| 11 | 1 8 9 10 | tngval | ⊢ ( ( 𝐺  ∈  V  ∧  𝑁  ∈  𝑉 )  →  𝑇  =  ( ( 𝐺  sSet  〈 ( dist ‘ ndx ) ,  ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) 〉 )  sSet  〈 ( TopSet ‘ ndx ) ,  ( MetOpen ‘ ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) ) 〉 ) ) | 
						
							| 12 | 11 | fveq2d | ⊢ ( ( 𝐺  ∈  V  ∧  𝑁  ∈  𝑉 )  →  ( 𝐸 ‘ 𝑇 )  =  ( 𝐸 ‘ ( ( 𝐺  sSet  〈 ( dist ‘ ndx ) ,  ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) 〉 )  sSet  〈 ( TopSet ‘ ndx ) ,  ( MetOpen ‘ ( 𝑁  ∘  ( -g ‘ 𝐺 ) ) ) 〉 ) ) ) | 
						
							| 13 | 7 12 | eqtr4id | ⊢ ( ( 𝐺  ∈  V  ∧  𝑁  ∈  𝑉 )  →  ( 𝐸 ‘ 𝐺 )  =  ( 𝐸 ‘ 𝑇 ) ) | 
						
							| 14 | 2 | str0 | ⊢ ∅  =  ( 𝐸 ‘ ∅ ) | 
						
							| 15 | 14 | eqcomi | ⊢ ( 𝐸 ‘ ∅ )  =  ∅ | 
						
							| 16 |  | reldmtng | ⊢ Rel  dom   toNrmGrp | 
						
							| 17 | 15 1 16 | oveqprc | ⊢ ( ¬  𝐺  ∈  V  →  ( 𝐸 ‘ 𝐺 )  =  ( 𝐸 ‘ 𝑇 ) ) | 
						
							| 18 | 17 | adantr | ⊢ ( ( ¬  𝐺  ∈  V  ∧  𝑁  ∈  𝑉 )  →  ( 𝐸 ‘ 𝐺 )  =  ( 𝐸 ‘ 𝑇 ) ) | 
						
							| 19 | 13 18 | pm2.61ian | ⊢ ( 𝑁  ∈  𝑉  →  ( 𝐸 ‘ 𝐺 )  =  ( 𝐸 ‘ 𝑇 ) ) |