Database SUPPLEMENTARY MATERIAL (USERS' MATHBOXES) Mathbox for Richard Penner Exploring Topology via Seifert and Threlfall Generic Pseudoclosure Spaces, Pseudointerior Spaces, and Pseudoneighborhoods ntrclsfv2  
				
		 
		
			
		 
		Description:   If (pseudo-)interior and (pseudo-)closure functions are related by the
         duality operator then there is a functional relation between them
         (Contributed by RP , 28-May-2021) 
		
			
				
					Ref 
					Expression 
				 
					
						Hypotheses 
						ntrcls.o ⊢  𝑂   =  ( 𝑖   ∈  V  ↦  ( 𝑘   ∈  ( 𝒫  𝑖   ↑m   𝒫  𝑖  )  ↦  ( 𝑗   ∈  𝒫  𝑖   ↦  ( 𝑖   ∖  ( 𝑘  ‘ ( 𝑖   ∖  𝑗  ) ) ) ) ) )  
					
						ntrcls.d ⊢  𝐷   =  ( 𝑂  ‘ 𝐵  )  
					
						ntrcls.r ⊢  ( 𝜑   →  𝐼  𝐷  𝐾  )  
				
					Assertion 
					ntrclsfv2 ⊢   ( 𝜑   →  ( 𝐷  ‘ 𝐾  )  =  𝐼  )  
			
		 
		
				Proof 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							1 
								
							 
							ntrcls.o ⊢  𝑂   =  ( 𝑖   ∈  V  ↦  ( 𝑘   ∈  ( 𝒫  𝑖   ↑m   𝒫  𝑖  )  ↦  ( 𝑗   ∈  𝒫  𝑖   ↦  ( 𝑖   ∖  ( 𝑘  ‘ ( 𝑖   ∖  𝑗  ) ) ) ) ) )  
						
							2 
								
							 
							ntrcls.d ⊢  𝐷   =  ( 𝑂  ‘ 𝐵  )  
						
							3 
								
							 
							ntrcls.r ⊢  ( 𝜑   →  𝐼  𝐷  𝐾  )  
						
							4 
								1  2  3 
							 
							ntrclsnvobr ⊢  ( 𝜑   →  𝐾  𝐷  𝐼  )  
						
							5 
								1  2  4 
							 
							ntrclsfv1 ⊢  ( 𝜑   →  ( 𝐷  ‘ 𝐾  )  =  𝐼  )