被积函数是x的奇函数,积分区间关于y轴对称,被积函数在积分区间上正负各半,该部分的积分就是0。当被积函数大于零时,二重积分是柱体的体积。当被积函数小于零时,二重积分是柱体体积负值。
同时二重积分有着广泛的应用,可以用来计算曲面的面积,平面薄片重心,平面薄片转动惯量,平面薄片对质点的引力等等。
![](https://iknow-pic.cdn.bcebos.com/4d086e061d950a7bcce23e1104d162d9f3d3c914?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
扩展资料:
二重积分的性质:
1、积分可加性:函数和(差)的二重积分等于各函数二重积分的和(差),即
![](https://iknow-pic.cdn.bcebos.com/b64543a98226cffcb35acf67b7014a90f703eaf7?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
2、积分满足数乘:被积函数的常系数因子可以提到积分号外,即
![](https://iknow-pic.cdn.bcebos.com/9a504fc2d5628535d1c1a2f49eef76c6a6ef63c5?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
3、比较性:如果在区域D上有f(x,y)≦g(x,y),则
![](https://iknow-pic.cdn.bcebos.com/86d6277f9e2f0708ed755ad5e724b899a801f2f7?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)