| Step | Hyp | Ref | Expression | 
						
							| 1 |  | lsmfval.v | ⊢ 𝐵  =  ( Base ‘ 𝐺 ) | 
						
							| 2 |  | lsmfval.a | ⊢  +   =  ( +g ‘ 𝐺 ) | 
						
							| 3 |  | lsmfval.s | ⊢  ⊕   =  ( LSSum ‘ 𝐺 ) | 
						
							| 4 | 1 2 3 | lsmfval | ⊢ ( 𝐺  ∈  𝑉  →   ⊕   =  ( 𝑡  ∈  𝒫  𝐵 ,  𝑢  ∈  𝒫  𝐵  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) ) ) ) | 
						
							| 5 | 4 | oveqd | ⊢ ( 𝐺  ∈  𝑉  →  ( 𝑇  ⊕  𝑈 )  =  ( 𝑇 ( 𝑡  ∈  𝒫  𝐵 ,  𝑢  ∈  𝒫  𝐵  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) ) ) 𝑈 ) ) | 
						
							| 6 | 1 | fvexi | ⊢ 𝐵  ∈  V | 
						
							| 7 | 6 | elpw2 | ⊢ ( 𝑇  ∈  𝒫  𝐵  ↔  𝑇  ⊆  𝐵 ) | 
						
							| 8 | 6 | elpw2 | ⊢ ( 𝑈  ∈  𝒫  𝐵  ↔  𝑈  ⊆  𝐵 ) | 
						
							| 9 |  | mpoexga | ⊢ ( ( 𝑇  ∈  𝒫  𝐵  ∧  𝑈  ∈  𝒫  𝐵 )  →  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) )  ∈  V ) | 
						
							| 10 |  | rnexg | ⊢ ( ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) )  ∈  V  →  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) )  ∈  V ) | 
						
							| 11 | 9 10 | syl | ⊢ ( ( 𝑇  ∈  𝒫  𝐵  ∧  𝑈  ∈  𝒫  𝐵 )  →  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) )  ∈  V ) | 
						
							| 12 |  | mpoeq12 | ⊢ ( ( 𝑡  =  𝑇  ∧  𝑢  =  𝑈 )  →  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) )  =  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) ) ) | 
						
							| 13 | 12 | rneqd | ⊢ ( ( 𝑡  =  𝑇  ∧  𝑢  =  𝑈 )  →  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) )  =  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) ) ) | 
						
							| 14 |  | eqid | ⊢ ( 𝑡  ∈  𝒫  𝐵 ,  𝑢  ∈  𝒫  𝐵  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) ) )  =  ( 𝑡  ∈  𝒫  𝐵 ,  𝑢  ∈  𝒫  𝐵  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) ) ) | 
						
							| 15 | 13 14 | ovmpoga | ⊢ ( ( 𝑇  ∈  𝒫  𝐵  ∧  𝑈  ∈  𝒫  𝐵  ∧  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) )  ∈  V )  →  ( 𝑇 ( 𝑡  ∈  𝒫  𝐵 ,  𝑢  ∈  𝒫  𝐵  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) ) ) 𝑈 )  =  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) ) ) | 
						
							| 16 | 11 15 | mpd3an3 | ⊢ ( ( 𝑇  ∈  𝒫  𝐵  ∧  𝑈  ∈  𝒫  𝐵 )  →  ( 𝑇 ( 𝑡  ∈  𝒫  𝐵 ,  𝑢  ∈  𝒫  𝐵  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) ) ) 𝑈 )  =  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) ) ) | 
						
							| 17 | 7 8 16 | syl2anbr | ⊢ ( ( 𝑇  ⊆  𝐵  ∧  𝑈  ⊆  𝐵 )  →  ( 𝑇 ( 𝑡  ∈  𝒫  𝐵 ,  𝑢  ∈  𝒫  𝐵  ↦  ran  ( 𝑥  ∈  𝑡 ,  𝑦  ∈  𝑢  ↦  ( 𝑥  +  𝑦 ) ) ) 𝑈 )  =  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) ) ) | 
						
							| 18 | 5 17 | sylan9eq | ⊢ ( ( 𝐺  ∈  𝑉  ∧  ( 𝑇  ⊆  𝐵  ∧  𝑈  ⊆  𝐵 ) )  →  ( 𝑇  ⊕  𝑈 )  =  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) ) ) | 
						
							| 19 | 18 | 3impb | ⊢ ( ( 𝐺  ∈  𝑉  ∧  𝑇  ⊆  𝐵  ∧  𝑈  ⊆  𝐵 )  →  ( 𝑇  ⊕  𝑈 )  =  ran  ( 𝑥  ∈  𝑇 ,  𝑦  ∈  𝑈  ↦  ( 𝑥  +  𝑦 ) ) ) |