| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dsmmelbas.p | ⊢ 𝑃  =  ( 𝑆 Xs 𝑅 ) | 
						
							| 2 |  | dsmmelbas.c | ⊢ 𝐶  =  ( 𝑆  ⊕m  𝑅 ) | 
						
							| 3 |  | dsmmelbas.b | ⊢ 𝐵  =  ( Base ‘ 𝑃 ) | 
						
							| 4 |  | dsmmelbas.h | ⊢ 𝐻  =  ( Base ‘ 𝐶 ) | 
						
							| 5 |  | dsmmelbas.i | ⊢ ( 𝜑  →  𝐼  ∈  𝑉 ) | 
						
							| 6 |  | dsmmelbas.r | ⊢ ( 𝜑  →  𝑅  Fn  𝐼 ) | 
						
							| 7 | 2 | fveq2i | ⊢ ( Base ‘ 𝐶 )  =  ( Base ‘ ( 𝑆  ⊕m  𝑅 ) ) | 
						
							| 8 | 4 7 | eqtri | ⊢ 𝐻  =  ( Base ‘ ( 𝑆  ⊕m  𝑅 ) ) | 
						
							| 9 |  | fnex | ⊢ ( ( 𝑅  Fn  𝐼  ∧  𝐼  ∈  𝑉 )  →  𝑅  ∈  V ) | 
						
							| 10 | 6 5 9 | syl2anc | ⊢ ( 𝜑  →  𝑅  ∈  V ) | 
						
							| 11 |  | eqid | ⊢ { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin }  =  { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin } | 
						
							| 12 | 11 | dsmmbase | ⊢ ( 𝑅  ∈  V  →  { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin }  =  ( Base ‘ ( 𝑆  ⊕m  𝑅 ) ) ) | 
						
							| 13 | 10 12 | syl | ⊢ ( 𝜑  →  { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin }  =  ( Base ‘ ( 𝑆  ⊕m  𝑅 ) ) ) | 
						
							| 14 | 8 13 | eqtr4id | ⊢ ( 𝜑  →  𝐻  =  { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin } ) | 
						
							| 15 | 14 | eleq2d | ⊢ ( 𝜑  →  ( 𝑋  ∈  𝐻  ↔  𝑋  ∈  { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin } ) ) | 
						
							| 16 |  | fveq1 | ⊢ ( 𝑏  =  𝑋  →  ( 𝑏 ‘ 𝑎 )  =  ( 𝑋 ‘ 𝑎 ) ) | 
						
							| 17 | 16 | neeq1d | ⊢ ( 𝑏  =  𝑋  →  ( ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) )  ↔  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) ) ) | 
						
							| 18 | 17 | rabbidv | ⊢ ( 𝑏  =  𝑋  →  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  =  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) } ) | 
						
							| 19 | 18 | eleq1d | ⊢ ( 𝑏  =  𝑋  →  ( { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin  ↔  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin ) ) | 
						
							| 20 | 19 | elrab | ⊢ ( 𝑋  ∈  { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin }  ↔  ( 𝑋  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∧  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin ) ) | 
						
							| 21 | 1 | fveq2i | ⊢ ( Base ‘ 𝑃 )  =  ( Base ‘ ( 𝑆 Xs 𝑅 ) ) | 
						
							| 22 | 3 21 | eqtr2i | ⊢ ( Base ‘ ( 𝑆 Xs 𝑅 ) )  =  𝐵 | 
						
							| 23 | 22 | eleq2i | ⊢ ( 𝑋  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ↔  𝑋  ∈  𝐵 ) | 
						
							| 24 | 23 | a1i | ⊢ ( 𝜑  →  ( 𝑋  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ↔  𝑋  ∈  𝐵 ) ) | 
						
							| 25 |  | fndm | ⊢ ( 𝑅  Fn  𝐼  →  dom  𝑅  =  𝐼 ) | 
						
							| 26 |  | rabeq | ⊢ ( dom  𝑅  =  𝐼  →  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  =  { 𝑎  ∈  𝐼  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) } ) | 
						
							| 27 | 6 25 26 | 3syl | ⊢ ( 𝜑  →  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  =  { 𝑎  ∈  𝐼  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) } ) | 
						
							| 28 | 27 | eleq1d | ⊢ ( 𝜑  →  ( { 𝑎  ∈  dom  𝑅  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin  ↔  { 𝑎  ∈  𝐼  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin ) ) | 
						
							| 29 | 24 28 | anbi12d | ⊢ ( 𝜑  →  ( ( 𝑋  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∧  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin )  ↔  ( 𝑋  ∈  𝐵  ∧  { 𝑎  ∈  𝐼  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin ) ) ) | 
						
							| 30 | 20 29 | bitrid | ⊢ ( 𝜑  →  ( 𝑋  ∈  { 𝑏  ∈  ( Base ‘ ( 𝑆 Xs 𝑅 ) )  ∣  { 𝑎  ∈  dom  𝑅  ∣  ( 𝑏 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin }  ↔  ( 𝑋  ∈  𝐵  ∧  { 𝑎  ∈  𝐼  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin ) ) ) | 
						
							| 31 | 15 30 | bitrd | ⊢ ( 𝜑  →  ( 𝑋  ∈  𝐻  ↔  ( 𝑋  ∈  𝐵  ∧  { 𝑎  ∈  𝐼  ∣  ( 𝑋 ‘ 𝑎 )  ≠  ( 0g ‘ ( 𝑅 ‘ 𝑎 ) ) }  ∈  Fin ) ) ) |