⑩天掌 Teaching Plan on Advanced Mathematics o 类似地定义 「Qxy)=1∑5,Ay 其中P(x,y),Q(x,y叫做被积函数,L叫积分弧段 tianjin polytechnic dmivendityTianjin Polytechnic University Teaching Plan on Advanced Mathematics 类似地定义 ( , ) lim ( , ) . 1 0 i i n i i L Q x y dy = Q y  = →    其中P(x, y), Q(x, y)叫做被积函数, L叫积分弧段