| Step | Hyp | Ref | Expression | 
						
							| 1 |  | eqid | ⊢ ( Base ‘ 𝑅 )  =  ( Base ‘ 𝑅 ) | 
						
							| 2 |  | eqid | ⊢ ( +g ‘ 𝑅 )  =  ( +g ‘ 𝑅 ) | 
						
							| 3 |  | eqid | ⊢ ( LSSum ‘ 𝑅 )  =  ( LSSum ‘ 𝑅 ) | 
						
							| 4 | 1 2 3 | lsmfval | ⊢ ( 𝑅  ∈  𝑉  →  ( LSSum ‘ 𝑅 )  =  ( 𝑡  ∈  𝒫  ( Base ‘ 𝑅 ) ,  𝑢  ∈  𝒫  ( Base ‘ 𝑅 )  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥 ( +g ‘ 𝑅 ) 𝑦 ) ) ) ) | 
						
							| 5 |  | fvex | ⊢ ( ringLMod ‘ 𝑅 )  ∈  V | 
						
							| 6 |  | rlmbas | ⊢ ( Base ‘ 𝑅 )  =  ( Base ‘ ( ringLMod ‘ 𝑅 ) ) | 
						
							| 7 |  | rlmplusg | ⊢ ( +g ‘ 𝑅 )  =  ( +g ‘ ( ringLMod ‘ 𝑅 ) ) | 
						
							| 8 |  | eqid | ⊢ ( LSSum ‘ ( ringLMod ‘ 𝑅 ) )  =  ( LSSum ‘ ( ringLMod ‘ 𝑅 ) ) | 
						
							| 9 | 6 7 8 | lsmfval | ⊢ ( ( ringLMod ‘ 𝑅 )  ∈  V  →  ( LSSum ‘ ( ringLMod ‘ 𝑅 ) )  =  ( 𝑡  ∈  𝒫  ( Base ‘ 𝑅 ) ,  𝑢  ∈  𝒫  ( Base ‘ 𝑅 )  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥 ( +g ‘ 𝑅 ) 𝑦 ) ) ) ) | 
						
							| 10 | 5 9 | mp1i | ⊢ ( 𝑅  ∈  𝑉  →  ( LSSum ‘ ( ringLMod ‘ 𝑅 ) )  =  ( 𝑡  ∈  𝒫  ( Base ‘ 𝑅 ) ,  𝑢  ∈  𝒫  ( Base ‘ 𝑅 )  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥 ( +g ‘ 𝑅 ) 𝑦 ) ) ) ) | 
						
							| 11 | 4 10 | eqtr4d | ⊢ ( 𝑅  ∈  𝑉  →  ( LSSum ‘ 𝑅 )  =  ( LSSum ‘ ( ringLMod ‘ 𝑅 ) ) ) |