Database ZF (ZERMELO-FRAENKEL) SET THEORY ZF Set Theory - add the Axiom of Power Sets Operations eloprabg  
				
		 
		
			
		 
		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