设<img src="https://static.zxtiku.com/wangke/imgs/topic/4fa3022a5eb369238498e1977c3bf0d9.jpg"/>是<img src="https://static.zxtiku.com/wangke/imgs/topic/1f2119ab7f9aa6174e9aeaa60940c3fb.jpg"/>平面上的闭区域<img src="https://static.zxtiku.com/wangke/imgs/topic/1c82399278cbd606d97d01565aecaf3a.jpg"/>的上侧，则<img src="https://static.zxtiku.com/wangke/imgs/topic/82f1b596a84f3f8a5f2cb95badc43659.jpg"/>（）。