| Step | Hyp | Ref | Expression | 
						
							| 1 |  | lplnset.b | ⊢ 𝐵  =  ( Base ‘ 𝐾 ) | 
						
							| 2 |  | lplnset.c | ⊢ 𝐶  =  (  ⋖  ‘ 𝐾 ) | 
						
							| 3 |  | lplnset.n | ⊢ 𝑁  =  ( LLines ‘ 𝐾 ) | 
						
							| 4 |  | lplnset.p | ⊢ 𝑃  =  ( LPlanes ‘ 𝐾 ) | 
						
							| 5 |  | elex | ⊢ ( 𝐾  ∈  𝐴  →  𝐾  ∈  V ) | 
						
							| 6 |  | fveq2 | ⊢ ( 𝑘  =  𝐾  →  ( Base ‘ 𝑘 )  =  ( Base ‘ 𝐾 ) ) | 
						
							| 7 | 6 1 | eqtr4di | ⊢ ( 𝑘  =  𝐾  →  ( Base ‘ 𝑘 )  =  𝐵 ) | 
						
							| 8 |  | fveq2 | ⊢ ( 𝑘  =  𝐾  →  ( LLines ‘ 𝑘 )  =  ( LLines ‘ 𝐾 ) ) | 
						
							| 9 | 8 3 | eqtr4di | ⊢ ( 𝑘  =  𝐾  →  ( LLines ‘ 𝑘 )  =  𝑁 ) | 
						
							| 10 |  | fveq2 | ⊢ ( 𝑘  =  𝐾  →  (  ⋖  ‘ 𝑘 )  =  (  ⋖  ‘ 𝐾 ) ) | 
						
							| 11 | 10 2 | eqtr4di | ⊢ ( 𝑘  =  𝐾  →  (  ⋖  ‘ 𝑘 )  =  𝐶 ) | 
						
							| 12 | 11 | breqd | ⊢ ( 𝑘  =  𝐾  →  ( 𝑦 (  ⋖  ‘ 𝑘 ) 𝑥  ↔  𝑦 𝐶 𝑥 ) ) | 
						
							| 13 | 9 12 | rexeqbidv | ⊢ ( 𝑘  =  𝐾  →  ( ∃ 𝑦  ∈  ( LLines ‘ 𝑘 ) 𝑦 (  ⋖  ‘ 𝑘 ) 𝑥  ↔  ∃ 𝑦  ∈  𝑁 𝑦 𝐶 𝑥 ) ) | 
						
							| 14 | 7 13 | rabeqbidv | ⊢ ( 𝑘  =  𝐾  →  { 𝑥  ∈  ( Base ‘ 𝑘 )  ∣  ∃ 𝑦  ∈  ( LLines ‘ 𝑘 ) 𝑦 (  ⋖  ‘ 𝑘 ) 𝑥 }  =  { 𝑥  ∈  𝐵  ∣  ∃ 𝑦  ∈  𝑁 𝑦 𝐶 𝑥 } ) | 
						
							| 15 |  | df-lplanes | ⊢ LPlanes  =  ( 𝑘  ∈  V  ↦  { 𝑥  ∈  ( Base ‘ 𝑘 )  ∣  ∃ 𝑦  ∈  ( LLines ‘ 𝑘 ) 𝑦 (  ⋖  ‘ 𝑘 ) 𝑥 } ) | 
						
							| 16 | 1 | fvexi | ⊢ 𝐵  ∈  V | 
						
							| 17 | 16 | rabex | ⊢ { 𝑥  ∈  𝐵  ∣  ∃ 𝑦  ∈  𝑁 𝑦 𝐶 𝑥 }  ∈  V | 
						
							| 18 | 14 15 17 | fvmpt | ⊢ ( 𝐾  ∈  V  →  ( LPlanes ‘ 𝐾 )  =  { 𝑥  ∈  𝐵  ∣  ∃ 𝑦  ∈  𝑁 𝑦 𝐶 𝑥 } ) | 
						
							| 19 | 4 18 | eqtrid | ⊢ ( 𝐾  ∈  V  →  𝑃  =  { 𝑥  ∈  𝐵  ∣  ∃ 𝑦  ∈  𝑁 𝑦 𝐶 𝑥 } ) | 
						
							| 20 | 5 19 | syl | ⊢ ( 𝐾  ∈  𝐴  →  𝑃  =  { 𝑥  ∈  𝐵  ∣  ∃ 𝑦  ∈  𝑁 𝑦 𝐶 𝑥 } ) |