| Step | Hyp | Ref | Expression | 
						
							| 1 |  | rngcbasALTV.c | ⊢ 𝐶  =  ( RngCatALTV ‘ 𝑈 ) | 
						
							| 2 |  | rngcbasALTV.b | ⊢ 𝐵  =  ( Base ‘ 𝐶 ) | 
						
							| 3 |  | rngcbasALTV.u | ⊢ ( 𝜑  →  𝑈  ∈  𝑉 ) | 
						
							| 4 |  | eqidd | ⊢ ( 𝜑  →  ( 𝑈  ∩  Rng )  =  ( 𝑈  ∩  Rng ) ) | 
						
							| 5 |  | eqidd | ⊢ ( 𝜑  →  ( 𝑥  ∈  ( 𝑈  ∩  Rng ) ,  𝑦  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑥  RngHom  𝑦 ) )  =  ( 𝑥  ∈  ( 𝑈  ∩  Rng ) ,  𝑦  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑥  RngHom  𝑦 ) ) ) | 
						
							| 6 |  | eqidd | ⊢ ( 𝜑  →  ( 𝑣  ∈  ( ( 𝑈  ∩  Rng )  ×  ( 𝑈  ∩  Rng ) ) ,  𝑧  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑓  ∈  ( ( 2nd  ‘ 𝑣 )  RngHom  𝑧 ) ,  𝑔  ∈  ( ( 1st  ‘ 𝑣 )  RngHom  ( 2nd  ‘ 𝑣 ) )  ↦  ( 𝑓  ∘  𝑔 ) ) )  =  ( 𝑣  ∈  ( ( 𝑈  ∩  Rng )  ×  ( 𝑈  ∩  Rng ) ) ,  𝑧  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑓  ∈  ( ( 2nd  ‘ 𝑣 )  RngHom  𝑧 ) ,  𝑔  ∈  ( ( 1st  ‘ 𝑣 )  RngHom  ( 2nd  ‘ 𝑣 ) )  ↦  ( 𝑓  ∘  𝑔 ) ) ) ) | 
						
							| 7 | 1 3 4 5 6 | rngcvalALTV | ⊢ ( 𝜑  →  𝐶  =  { 〈 ( Base ‘ ndx ) ,  ( 𝑈  ∩  Rng ) 〉 ,  〈 ( Hom  ‘ ndx ) ,  ( 𝑥  ∈  ( 𝑈  ∩  Rng ) ,  𝑦  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑥  RngHom  𝑦 ) ) 〉 ,  〈 ( comp ‘ ndx ) ,  ( 𝑣  ∈  ( ( 𝑈  ∩  Rng )  ×  ( 𝑈  ∩  Rng ) ) ,  𝑧  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑓  ∈  ( ( 2nd  ‘ 𝑣 )  RngHom  𝑧 ) ,  𝑔  ∈  ( ( 1st  ‘ 𝑣 )  RngHom  ( 2nd  ‘ 𝑣 ) )  ↦  ( 𝑓  ∘  𝑔 ) ) ) 〉 } ) | 
						
							| 8 |  | catstr | ⊢ { 〈 ( Base ‘ ndx ) ,  ( 𝑈  ∩  Rng ) 〉 ,  〈 ( Hom  ‘ ndx ) ,  ( 𝑥  ∈  ( 𝑈  ∩  Rng ) ,  𝑦  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑥  RngHom  𝑦 ) ) 〉 ,  〈 ( comp ‘ ndx ) ,  ( 𝑣  ∈  ( ( 𝑈  ∩  Rng )  ×  ( 𝑈  ∩  Rng ) ) ,  𝑧  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑓  ∈  ( ( 2nd  ‘ 𝑣 )  RngHom  𝑧 ) ,  𝑔  ∈  ( ( 1st  ‘ 𝑣 )  RngHom  ( 2nd  ‘ 𝑣 ) )  ↦  ( 𝑓  ∘  𝑔 ) ) ) 〉 }  Struct  〈 1 ,  ; 1 5 〉 | 
						
							| 9 |  | baseid | ⊢ Base  =  Slot  ( Base ‘ ndx ) | 
						
							| 10 |  | snsstp1 | ⊢ { 〈 ( Base ‘ ndx ) ,  ( 𝑈  ∩  Rng ) 〉 }  ⊆  { 〈 ( Base ‘ ndx ) ,  ( 𝑈  ∩  Rng ) 〉 ,  〈 ( Hom  ‘ ndx ) ,  ( 𝑥  ∈  ( 𝑈  ∩  Rng ) ,  𝑦  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑥  RngHom  𝑦 ) ) 〉 ,  〈 ( comp ‘ ndx ) ,  ( 𝑣  ∈  ( ( 𝑈  ∩  Rng )  ×  ( 𝑈  ∩  Rng ) ) ,  𝑧  ∈  ( 𝑈  ∩  Rng )  ↦  ( 𝑓  ∈  ( ( 2nd  ‘ 𝑣 )  RngHom  𝑧 ) ,  𝑔  ∈  ( ( 1st  ‘ 𝑣 )  RngHom  ( 2nd  ‘ 𝑣 ) )  ↦  ( 𝑓  ∘  𝑔 ) ) ) 〉 } | 
						
							| 11 |  | inex1g | ⊢ ( 𝑈  ∈  𝑉  →  ( 𝑈  ∩  Rng )  ∈  V ) | 
						
							| 12 | 3 11 | syl | ⊢ ( 𝜑  →  ( 𝑈  ∩  Rng )  ∈  V ) | 
						
							| 13 | 7 8 9 10 12 2 | strfv3 | ⊢ ( 𝜑  →  𝐵  =  ( 𝑈  ∩  Rng ) ) |