| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							fnbrovb | 
							 |-  ( ( F Fn ( A X. B ) /\ ( C e. A /\ D e. B ) ) -> ( ( C F D ) = R <-> <. C , D >. F R ) )  | 
						
						
							| 2 | 
							
								
							 | 
							df-br | 
							 |-  ( <. C , D >. F R <-> <. <. C , D >. , R >. e. F )  | 
						
						
							| 3 | 
							
								2
							 | 
							a1i | 
							 |-  ( ( F Fn ( A X. B ) /\ ( C e. A /\ D e. B ) ) -> ( <. C , D >. F R <-> <. <. C , D >. , R >. e. F ) )  | 
						
						
							| 4 | 
							
								
							 | 
							df-ot | 
							 |-  <. C , D , R >. = <. <. C , D >. , R >.  | 
						
						
							| 5 | 
							
								4
							 | 
							eqcomi | 
							 |-  <. <. C , D >. , R >. = <. C , D , R >.  | 
						
						
							| 6 | 
							
								5
							 | 
							eleq1i | 
							 |-  ( <. <. C , D >. , R >. e. F <-> <. C , D , R >. e. F )  | 
						
						
							| 7 | 
							
								6
							 | 
							a1i | 
							 |-  ( ( F Fn ( A X. B ) /\ ( C e. A /\ D e. B ) ) -> ( <. <. C , D >. , R >. e. F <-> <. C , D , R >. e. F ) )  | 
						
						
							| 8 | 
							
								1 3 7
							 | 
							3bitrd | 
							 |-  ( ( F Fn ( A X. B ) /\ ( C e. A /\ D e. B ) ) -> ( ( C F D ) = R <-> <. C , D , R >. e. F ) )  | 
						
						
							| 9 | 
							
								8
							 | 
							3impb | 
							 |-  ( ( F Fn ( A X. B ) /\ C e. A /\ D e. B ) -> ( ( C F D ) = R <-> <. C , D , R >. e. F ) )  |