Database ZF (ZERMELO-FRAENKEL) SET THEORY ZF Set Theory - start with the Axiom of Extensionality Restricted quantification Restricted universal and existential quantification raleqbii  
				
		 
		
			
		 
		Description:   Equality deduction for restricted universal quantifier, changing both
       formula and quantifier domain.  Inference form.  (Contributed by David
       Moews , 1-May-2017) 
		
			
				
					Ref 
					Expression 
				 
					
						Hypotheses 
						raleqbii.1   ⊢   A  =  B       
					 
					
						raleqbii.2    ⊢   ψ   ↔   χ        
					 
				
					Assertion 
					raleqbii    ⊢   ∀  x  ∈  A   ψ     ↔   ∀  x  ∈  B   χ          
				 
			
		 
		
				Proof 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							1 
								
							 
							raleqbii.1  ⊢   A  =  B       
						
							2 
								
							 
							raleqbii.2   ⊢   ψ   ↔   χ        
						
							3 
								1 
							 
							eleq2i   ⊢   x  ∈  A    ↔   x  ∈  B         
						
							4 
								3  2 
							 
							imbi12i   ⊢    x  ∈  A    →   ψ    ↔    x  ∈  B    →   χ         
						
							5 
								4 
							 
							ralbii2   ⊢   ∀  x  ∈  A   ψ     ↔   ∀  x  ∈  B   χ