Database  
				SUPPLEMENTARY MATERIAL (USERS' MATHBOXES)  
				Mathbox for Steven Nguyen  
				Structures  
				pwselbasr  
			 
				
		 
		 Metamath Proof Explorer 
		
			
		 
		 
		
		Description:   The reverse direction of pwselbasb  : a function between the index and
       base set of a structure is an element of the structure power.
       (Contributed by SN , 29-Jul-2024) 
		
			
				
					 
					 
					Ref 
					Expression 
				 
					
						 
						Hypotheses 
						pwselbasr.y  
						  ⊢   Y  =  R  ↑  𝑠   I          
					 
					
						 
						 
						pwselbasr.b  
						  ⊢   B  =  Base  R          
					 
					
						 
						 
						pwselbasr.v  
						  ⊢   V  =  Base  Y          
					 
					
						 
						 
						pwselbasr.r  
						   ⊢   φ   →   R  ∈  W         
					 
					
						 
						 
						pwselbasr.i  
						   ⊢   φ   →   I  ∈  Z         
					 
					
						 
						 
						pwselbasr.x  
						   ⊢   φ   →   X  :  I  ⟶  B         
					 
				
					 
					Assertion 
					pwselbasr  
					   ⊢   φ   →   X  ∈  V         
				 
			
		 
		 
			
				Proof 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							1  
							
								
							 
							pwselbasr.y  
							   ⊢   Y  =  R  ↑  𝑠   I          
						 
						
							2  
							
								
							 
							pwselbasr.b  
							   ⊢   B  =  Base  R          
						 
						
							3  
							
								
							 
							pwselbasr.v  
							   ⊢   V  =  Base  Y          
						 
						
							4  
							
								
							 
							pwselbasr.r  
							    ⊢   φ   →   R  ∈  W         
						 
						
							5  
							
								
							 
							pwselbasr.i  
							    ⊢   φ   →   I  ∈  Z         
						 
						
							6  
							
								
							 
							pwselbasr.x  
							    ⊢   φ   →   X  :  I  ⟶  B         
						 
						
							7  
							
								1  2  3 
							 
							pwselbasb  
							    ⊢    R  ∈  W    ∧   I  ∈  Z       →    X  ∈  V    ↔   X  :  I  ⟶  B            
						 
						
							8  
							
								4  5  7 
							 
							syl2anc  
							    ⊢   φ   →    X  ∈  V    ↔   X  :  I  ⟶  B            
						 
						
							9  
							
								6  8 
							 
							mpbird  
							    ⊢   φ   →   X  ∈  V