引言 由定积分定义 f(x)=m。∑f(5)△x i=0 (1)分割a=x0<x<…<xn=;b (2)近似△,=f()△x1△x1=x1-x-1 (3)求和S,=∑△=∑f(5)△ i=0引言 ◼ 由定积分定义 i n i i n i n i i i i i i n i b a i n i i x S s f x s f x x x x a x x x b f x dx f x     = = − =  → =  =   =   = − =    = =  0 0 1 0 1 0 0 (3) ( ) (2) ( ) (1) ... ( ) lim ( )    求和 近似 分割