| Step | Hyp | Ref | Expression | 
						
							| 1 |  | nfitg.1 |  |-  F/_ y A | 
						
							| 2 |  | nfitg.2 |  |-  F/_ y B | 
						
							| 3 |  | eqid |  |-  ( Re ` ( B / ( _i ^ k ) ) ) = ( Re ` ( B / ( _i ^ k ) ) ) | 
						
							| 4 | 3 | dfitg |  |-  S. A B _d x = sum_ k e. ( 0 ... 3 ) ( ( _i ^ k ) x. ( S.2 ` ( x e. RR |-> if ( ( x e. A /\ 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) ) , ( Re ` ( B / ( _i ^ k ) ) ) , 0 ) ) ) ) | 
						
							| 5 |  | nfcv |  |-  F/_ y ( 0 ... 3 ) | 
						
							| 6 |  | nfcv |  |-  F/_ y ( _i ^ k ) | 
						
							| 7 |  | nfcv |  |-  F/_ y x. | 
						
							| 8 |  | nfcv |  |-  F/_ y S.2 | 
						
							| 9 |  | nfcv |  |-  F/_ y RR | 
						
							| 10 | 1 | nfcri |  |-  F/ y x e. A | 
						
							| 11 |  | nfcv |  |-  F/_ y 0 | 
						
							| 12 |  | nfcv |  |-  F/_ y <_ | 
						
							| 13 |  | nfcv |  |-  F/_ y Re | 
						
							| 14 |  | nfcv |  |-  F/_ y / | 
						
							| 15 | 2 14 6 | nfov |  |-  F/_ y ( B / ( _i ^ k ) ) | 
						
							| 16 | 13 15 | nffv |  |-  F/_ y ( Re ` ( B / ( _i ^ k ) ) ) | 
						
							| 17 | 11 12 16 | nfbr |  |-  F/ y 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) | 
						
							| 18 | 10 17 | nfan |  |-  F/ y ( x e. A /\ 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) ) | 
						
							| 19 | 18 16 11 | nfif |  |-  F/_ y if ( ( x e. A /\ 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) ) , ( Re ` ( B / ( _i ^ k ) ) ) , 0 ) | 
						
							| 20 | 9 19 | nfmpt |  |-  F/_ y ( x e. RR |-> if ( ( x e. A /\ 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) ) , ( Re ` ( B / ( _i ^ k ) ) ) , 0 ) ) | 
						
							| 21 | 8 20 | nffv |  |-  F/_ y ( S.2 ` ( x e. RR |-> if ( ( x e. A /\ 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) ) , ( Re ` ( B / ( _i ^ k ) ) ) , 0 ) ) ) | 
						
							| 22 | 6 7 21 | nfov |  |-  F/_ y ( ( _i ^ k ) x. ( S.2 ` ( x e. RR |-> if ( ( x e. A /\ 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) ) , ( Re ` ( B / ( _i ^ k ) ) ) , 0 ) ) ) ) | 
						
							| 23 | 5 22 | nfsum |  |-  F/_ y sum_ k e. ( 0 ... 3 ) ( ( _i ^ k ) x. ( S.2 ` ( x e. RR |-> if ( ( x e. A /\ 0 <_ ( Re ` ( B / ( _i ^ k ) ) ) ) , ( Re ` ( B / ( _i ^ k ) ) ) , 0 ) ) ) ) | 
						
							| 24 | 4 23 | nfcxfr |  |-  F/_ y S. A B _d x |