Database  
				ZF (ZERMELO-FRAENKEL) SET THEORY  
				ZF Set Theory - add the Axiom of Power Sets  
				Operations  
				eloprabg  
			 
				
		 
		 Metamath Proof Explorer 
		
			
		 
		 
		
		Description:   The law of concretion for operation class abstraction.  Compare
       elopab  .  (Contributed by NM , 14-Sep-1999)   (Revised by David
       Abernethy , 19-Jun-2012) 
		
			
				
					 
					 
					Ref 
					Expression 
				 
					
						 
						Hypotheses 
						eloprabg.1  
						   ⊢   x  =  A    →    φ   ↔   ψ           
					 
					
						 
						 
						eloprabg.2  
						   ⊢   y  =  B    →    ψ   ↔   χ           
					 
					
						 
						 
						eloprabg.3  
						   ⊢   z  =  C    →    χ   ↔   θ           
					 
				
					 
					Assertion 
					eloprabg  
					   ⊢    A  ∈  V    ∧   B  ∈  W    ∧   C  ∈  X       →      A  B    C    ∈   x  y   z   |   φ       ↔   θ           
				 
			
		 
		 
			
				Proof 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							1  
							
								
							 
							eloprabg.1  
							    ⊢   x  =  A    →    φ   ↔   ψ           
						 
						
							2  
							
								
							 
							eloprabg.2  
							    ⊢   y  =  B    →    ψ   ↔   χ           
						 
						
							3  
							
								
							 
							eloprabg.3  
							    ⊢   z  =  C    →    χ   ↔   θ           
						 
						
							4  
							
								1  2  3 
							 
							syl3an9b  
							    ⊢    x  =  A    ∧   y  =  B    ∧   z  =  C       →    φ   ↔   θ           
						 
						
							5  
							
								4 
							 
							eloprabga  
							    ⊢    A  ∈  V    ∧   B  ∈  W    ∧   C  ∈  X       →      A  B    C    ∈   x  y   z   |   φ       ↔   θ