| Step | Hyp | Ref | Expression | 
						
							| 1 |  | oppggic.o | ⊢ 𝑂  =  ( oppg ‘ 𝐺 ) | 
						
							| 2 |  | submrcl | ⊢ ( 𝑥  ∈  ( SubMnd ‘ 𝐺 )  →  𝐺  ∈  Mnd ) | 
						
							| 3 |  | submrcl | ⊢ ( 𝑥  ∈  ( SubMnd ‘ 𝑂 )  →  𝑂  ∈  Mnd ) | 
						
							| 4 | 1 | oppgmndb | ⊢ ( 𝐺  ∈  Mnd  ↔  𝑂  ∈  Mnd ) | 
						
							| 5 | 3 4 | sylibr | ⊢ ( 𝑥  ∈  ( SubMnd ‘ 𝑂 )  →  𝐺  ∈  Mnd ) | 
						
							| 6 |  | ralcom | ⊢ ( ∀ 𝑦  ∈  𝑥 ∀ 𝑧  ∈  𝑥 ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥  ↔  ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥 ) | 
						
							| 7 |  | eqid | ⊢ ( +g ‘ 𝐺 )  =  ( +g ‘ 𝐺 ) | 
						
							| 8 |  | eqid | ⊢ ( +g ‘ 𝑂 )  =  ( +g ‘ 𝑂 ) | 
						
							| 9 | 7 1 8 | oppgplus | ⊢ ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  =  ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 ) | 
						
							| 10 | 9 | eleq1i | ⊢ ( ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  ∈  𝑥  ↔  ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥 ) | 
						
							| 11 | 10 | 2ralbii | ⊢ ( ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  ∈  𝑥  ↔  ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥 ) | 
						
							| 12 | 6 11 | bitr4i | ⊢ ( ∀ 𝑦  ∈  𝑥 ∀ 𝑧  ∈  𝑥 ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥  ↔  ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  ∈  𝑥 ) | 
						
							| 13 | 12 | 3anbi3i | ⊢ ( ( 𝑥  ⊆  ( Base ‘ 𝐺 )  ∧  ( 0g ‘ 𝐺 )  ∈  𝑥  ∧  ∀ 𝑦  ∈  𝑥 ∀ 𝑧  ∈  𝑥 ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥 )  ↔  ( 𝑥  ⊆  ( Base ‘ 𝐺 )  ∧  ( 0g ‘ 𝐺 )  ∈  𝑥  ∧  ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  ∈  𝑥 ) ) | 
						
							| 14 | 13 | a1i | ⊢ ( 𝐺  ∈  Mnd  →  ( ( 𝑥  ⊆  ( Base ‘ 𝐺 )  ∧  ( 0g ‘ 𝐺 )  ∈  𝑥  ∧  ∀ 𝑦  ∈  𝑥 ∀ 𝑧  ∈  𝑥 ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥 )  ↔  ( 𝑥  ⊆  ( Base ‘ 𝐺 )  ∧  ( 0g ‘ 𝐺 )  ∈  𝑥  ∧  ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  ∈  𝑥 ) ) ) | 
						
							| 15 |  | eqid | ⊢ ( Base ‘ 𝐺 )  =  ( Base ‘ 𝐺 ) | 
						
							| 16 |  | eqid | ⊢ ( 0g ‘ 𝐺 )  =  ( 0g ‘ 𝐺 ) | 
						
							| 17 | 15 16 7 | issubm | ⊢ ( 𝐺  ∈  Mnd  →  ( 𝑥  ∈  ( SubMnd ‘ 𝐺 )  ↔  ( 𝑥  ⊆  ( Base ‘ 𝐺 )  ∧  ( 0g ‘ 𝐺 )  ∈  𝑥  ∧  ∀ 𝑦  ∈  𝑥 ∀ 𝑧  ∈  𝑥 ( 𝑦 ( +g ‘ 𝐺 ) 𝑧 )  ∈  𝑥 ) ) ) | 
						
							| 18 | 1 15 | oppgbas | ⊢ ( Base ‘ 𝐺 )  =  ( Base ‘ 𝑂 ) | 
						
							| 19 | 1 16 | oppgid | ⊢ ( 0g ‘ 𝐺 )  =  ( 0g ‘ 𝑂 ) | 
						
							| 20 | 18 19 8 | issubm | ⊢ ( 𝑂  ∈  Mnd  →  ( 𝑥  ∈  ( SubMnd ‘ 𝑂 )  ↔  ( 𝑥  ⊆  ( Base ‘ 𝐺 )  ∧  ( 0g ‘ 𝐺 )  ∈  𝑥  ∧  ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  ∈  𝑥 ) ) ) | 
						
							| 21 | 4 20 | sylbi | ⊢ ( 𝐺  ∈  Mnd  →  ( 𝑥  ∈  ( SubMnd ‘ 𝑂 )  ↔  ( 𝑥  ⊆  ( Base ‘ 𝐺 )  ∧  ( 0g ‘ 𝐺 )  ∈  𝑥  ∧  ∀ 𝑧  ∈  𝑥 ∀ 𝑦  ∈  𝑥 ( 𝑧 ( +g ‘ 𝑂 ) 𝑦 )  ∈  𝑥 ) ) ) | 
						
							| 22 | 14 17 21 | 3bitr4d | ⊢ ( 𝐺  ∈  Mnd  →  ( 𝑥  ∈  ( SubMnd ‘ 𝐺 )  ↔  𝑥  ∈  ( SubMnd ‘ 𝑂 ) ) ) | 
						
							| 23 | 2 5 22 | pm5.21nii | ⊢ ( 𝑥  ∈  ( SubMnd ‘ 𝐺 )  ↔  𝑥  ∈  ( SubMnd ‘ 𝑂 ) ) | 
						
							| 24 | 23 | eqriv | ⊢ ( SubMnd ‘ 𝐺 )  =  ( SubMnd ‘ 𝑂 ) |