Database ZF (ZERMELO-FRAENKEL) SET THEORY ZF Set Theory - start with the Axiom of Extensionality The difference, union, and intersection of two classes The symmetric difference of two classes df-symdif  
				
		 
		
			
		 
		Description:   Define the symmetric difference of two classes.  Alternate definitions are
     dfsymdif2  , dfsymdif3  and dfsymdif4  .  (Contributed by Scott Fenton , 31-Mar-2012) 
		
			
				
					Ref 
					Expression 
				 
				
					Assertion 
					df-symdif   ⊢   A   ∆   B =    A  ∖  B   ∪   B  ∖  A          
				 
			
		 
		
				Detailed syntax breakdown 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							0 
								
							 
							cA  class  A    
						
							1 
								
							 
							cB  class  B    
						
							2 
								0  1 
							 
							csymdif  class  A   ∆   B    
						
							3 
								0  1 
							 
							cdif  class   A  ∖  B      
						
							4 
								1  0 
							 
							cdif  class   B  ∖  A      
						
							5 
								3  4 
							 
							cun  class    A  ∖  B   ∪   B  ∖  A       
						
							6 
								2  5 
							 
							wceq  wff   A   ∆   B =    A  ∖  B   ∪   B  ∖  A