| Step | Hyp | Ref | Expression | 
						
							| 1 |  | issubrng.b | ⊢ 𝐵  =  ( Base ‘ 𝑅 ) | 
						
							| 2 |  | df-subrng | ⊢ SubRng  =  ( 𝑤  ∈  Rng  ↦  { 𝑠  ∈  𝒫  ( Base ‘ 𝑤 )  ∣  ( 𝑤  ↾s  𝑠 )  ∈  Rng } ) | 
						
							| 3 | 2 | mptrcl | ⊢ ( 𝐴  ∈  ( SubRng ‘ 𝑅 )  →  𝑅  ∈  Rng ) | 
						
							| 4 |  | simp1 | ⊢ ( ( 𝑅  ∈  Rng  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 )  →  𝑅  ∈  Rng ) | 
						
							| 5 |  | fveq2 | ⊢ ( 𝑟  =  𝑅  →  ( Base ‘ 𝑟 )  =  ( Base ‘ 𝑅 ) ) | 
						
							| 6 | 5 | pweqd | ⊢ ( 𝑟  =  𝑅  →  𝒫  ( Base ‘ 𝑟 )  =  𝒫  ( Base ‘ 𝑅 ) ) | 
						
							| 7 |  | oveq1 | ⊢ ( 𝑟  =  𝑅  →  ( 𝑟  ↾s  𝑠 )  =  ( 𝑅  ↾s  𝑠 ) ) | 
						
							| 8 | 7 | eleq1d | ⊢ ( 𝑟  =  𝑅  →  ( ( 𝑟  ↾s  𝑠 )  ∈  Rng  ↔  ( 𝑅  ↾s  𝑠 )  ∈  Rng ) ) | 
						
							| 9 | 6 8 | rabeqbidv | ⊢ ( 𝑟  =  𝑅  →  { 𝑠  ∈  𝒫  ( Base ‘ 𝑟 )  ∣  ( 𝑟  ↾s  𝑠 )  ∈  Rng }  =  { 𝑠  ∈  𝒫  ( Base ‘ 𝑅 )  ∣  ( 𝑅  ↾s  𝑠 )  ∈  Rng } ) | 
						
							| 10 |  | df-subrng | ⊢ SubRng  =  ( 𝑟  ∈  Rng  ↦  { 𝑠  ∈  𝒫  ( Base ‘ 𝑟 )  ∣  ( 𝑟  ↾s  𝑠 )  ∈  Rng } ) | 
						
							| 11 |  | fvex | ⊢ ( Base ‘ 𝑅 )  ∈  V | 
						
							| 12 | 11 | pwex | ⊢ 𝒫  ( Base ‘ 𝑅 )  ∈  V | 
						
							| 13 | 12 | rabex | ⊢ { 𝑠  ∈  𝒫  ( Base ‘ 𝑅 )  ∣  ( 𝑅  ↾s  𝑠 )  ∈  Rng }  ∈  V | 
						
							| 14 | 9 10 13 | fvmpt | ⊢ ( 𝑅  ∈  Rng  →  ( SubRng ‘ 𝑅 )  =  { 𝑠  ∈  𝒫  ( Base ‘ 𝑅 )  ∣  ( 𝑅  ↾s  𝑠 )  ∈  Rng } ) | 
						
							| 15 | 14 | eleq2d | ⊢ ( 𝑅  ∈  Rng  →  ( 𝐴  ∈  ( SubRng ‘ 𝑅 )  ↔  𝐴  ∈  { 𝑠  ∈  𝒫  ( Base ‘ 𝑅 )  ∣  ( 𝑅  ↾s  𝑠 )  ∈  Rng } ) ) | 
						
							| 16 |  | oveq2 | ⊢ ( 𝑠  =  𝐴  →  ( 𝑅  ↾s  𝑠 )  =  ( 𝑅  ↾s  𝐴 ) ) | 
						
							| 17 | 16 | eleq1d | ⊢ ( 𝑠  =  𝐴  →  ( ( 𝑅  ↾s  𝑠 )  ∈  Rng  ↔  ( 𝑅  ↾s  𝐴 )  ∈  Rng ) ) | 
						
							| 18 | 17 | elrab | ⊢ ( 𝐴  ∈  { 𝑠  ∈  𝒫  ( Base ‘ 𝑅 )  ∣  ( 𝑅  ↾s  𝑠 )  ∈  Rng }  ↔  ( 𝐴  ∈  𝒫  ( Base ‘ 𝑅 )  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng ) ) | 
						
							| 19 | 1 | eqcomi | ⊢ ( Base ‘ 𝑅 )  =  𝐵 | 
						
							| 20 | 19 | sseq2i | ⊢ ( 𝐴  ⊆  ( Base ‘ 𝑅 )  ↔  𝐴  ⊆  𝐵 ) | 
						
							| 21 | 20 | anbi2i | ⊢ ( ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  ( Base ‘ 𝑅 ) )  ↔  ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) | 
						
							| 22 |  | ibar | ⊢ ( 𝑅  ∈  Rng  →  ( ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 )  ↔  ( 𝑅  ∈  Rng  ∧  ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) ) ) | 
						
							| 23 | 21 22 | bitrid | ⊢ ( 𝑅  ∈  Rng  →  ( ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  ( Base ‘ 𝑅 ) )  ↔  ( 𝑅  ∈  Rng  ∧  ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) ) ) | 
						
							| 24 | 11 | elpw2 | ⊢ ( 𝐴  ∈  𝒫  ( Base ‘ 𝑅 )  ↔  𝐴  ⊆  ( Base ‘ 𝑅 ) ) | 
						
							| 25 | 24 | anbi2ci | ⊢ ( ( 𝐴  ∈  𝒫  ( Base ‘ 𝑅 )  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng )  ↔  ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  ( Base ‘ 𝑅 ) ) ) | 
						
							| 26 |  | 3anass | ⊢ ( ( 𝑅  ∈  Rng  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 )  ↔  ( 𝑅  ∈  Rng  ∧  ( ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) ) | 
						
							| 27 | 23 25 26 | 3bitr4g | ⊢ ( 𝑅  ∈  Rng  →  ( ( 𝐴  ∈  𝒫  ( Base ‘ 𝑅 )  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng )  ↔  ( 𝑅  ∈  Rng  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) ) | 
						
							| 28 | 18 27 | bitrid | ⊢ ( 𝑅  ∈  Rng  →  ( 𝐴  ∈  { 𝑠  ∈  𝒫  ( Base ‘ 𝑅 )  ∣  ( 𝑅  ↾s  𝑠 )  ∈  Rng }  ↔  ( 𝑅  ∈  Rng  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) ) | 
						
							| 29 | 15 28 | bitrd | ⊢ ( 𝑅  ∈  Rng  →  ( 𝐴  ∈  ( SubRng ‘ 𝑅 )  ↔  ( 𝑅  ∈  Rng  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) ) | 
						
							| 30 | 3 4 29 | pm5.21nii | ⊢ ( 𝐴  ∈  ( SubRng ‘ 𝑅 )  ↔  ( 𝑅  ∈  Rng  ∧  ( 𝑅  ↾s  𝐴 )  ∈  Rng  ∧  𝐴  ⊆  𝐵 ) ) |