| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							atelch | 
							 |-  ( B e. HAtoms -> B e. CH )  | 
						
						
							| 2 | 
							
								
							 | 
							chincl | 
							 |-  ( ( A e. CH /\ B e. CH ) -> ( A i^i B ) e. CH )  | 
						
						
							| 3 | 
							
								1 2
							 | 
							sylan2 | 
							 |-  ( ( A e. CH /\ B e. HAtoms ) -> ( A i^i B ) e. CH )  | 
						
						
							| 4 | 
							
								
							 | 
							atcveq0 | 
							 |-  ( ( ( A i^i B ) e. CH /\ B e. HAtoms ) -> ( ( A i^i B )  ( A i^i B ) = 0H ) )  | 
						
						
							| 5 | 
							
								3 4
							 | 
							sylancom | 
							 |-  ( ( A e. CH /\ B e. HAtoms ) -> ( ( A i^i B )  ( A i^i B ) = 0H ) )  | 
						
						
							| 6 | 
							
								
							 | 
							cvexch | 
							 |-  ( ( A e. CH /\ B e. CH ) -> ( ( A i^i B )  A   | 
						
						
							| 7 | 
							
								1 6
							 | 
							sylan2 | 
							 |-  ( ( A e. CH /\ B e. HAtoms ) -> ( ( A i^i B )  A   | 
						
						
							| 8 | 
							
								5 7
							 | 
							bitr3d | 
							 |-  ( ( A e. CH /\ B e. HAtoms ) -> ( ( A i^i B ) = 0H <-> A   |