4.积分性质 如果当→+时,g(O)=f(dt→0 则f(0dt [f(切).(1.19 证因为 dt f(tdt=f(t) If(]=jo. f(t)dt9 4. 积分性质     = = =     → +  = →     - - - - t t t t f t f t t f t t f t t f t t f t t g t f t t [ ( )] j ( )d ( )d ( ), d d [ ( )]. (1.19) j 1 ( )d , ( ) ( )d 0 F F F F w w 证 因为 则 如果当 时