2 66 及 63 于是,得北积 分的近似值为 t yds +÷+2 ] 63 0.577-0.816+2.0913)亠0.402, 其精确值为 +ydus ya) (1 )d 0.4 3905.把域S{x2+y2≤1}分为有限个直径小于δ的订求积的 子域ASi(=1,2,…,n).对于什么样的值δ能保证不 等式 sin(+y)dS->sin(x, +y, AS <0.l 成立?其中(x;,y)∈△S; 解记函数sin(x+y)在△S2中的振幅为c,则 sin(+ y)ds sin(x,+y;)△S Csin(a t y)- sin(x, y. )]ds Isin(x + y)sin(x, +y, )ds