若函数<img src="https://static.zxtiku.com/wangke/imgs/topic/9afa31d39a6817ea09afaca079ae4b38.png"/>在空间可求面积的曲面<img src="https://static.zxtiku.com/wangke/imgs/topic/3294eb90da88d436c1bcf40a0ab93076.png"/>上的第一型曲面积分存在，<br/> 且<img src="https://static.zxtiku.com/wangke/imgs/topic/72ae8cdfc9039c8650eaf2dc536c46f7.png"/>,<br/> 则<img src="https://static.zxtiku.com/wangke/imgs/topic/e93746467e28eb3fbee6c06842837c6a.png"/>