设图1是坑的断面与俯视图,坑面最长的距离用AB表示,将AB分成n等份,每份长記为a,过各个分点作AB的垂直平面(A点或B点除外),并把各垂直平面在坑面与坑底间的部分之面积分別記为S_1,S_2,S_3,…,S_n,則坑的容积V的近似值可表示为: a(S_1+S_2+S_3+…+S_n),当将垂直平面与坑面交成的各个线段分成长为b的若干等分时,則有 Let Fig. 1 be the cross-section and top view of the pit. The longest distance to the pit surface is denoted by AB. Divide AB into n equal parts. Each length is denoted as a. Except for point A or B, the vertical plane of each point is AB. ), and the area of ​​the vertical plane between the pit surface and the pit bottom is denoted as S_1, S_2, S_3,..., S_n, respectively. The approximate value of the volume V of the pit can be expressed as: a(S_1+S_2+S_3+... +S_n), when the line segments intersecting the vertical plane with the pit face are divided into several equal parts of b, there are