若函数<img src="https://static.zxtiku.com/wangke/imgs/topic/96f9c4612fa478124c37d819c10ec5b0.png"/>在点<img src="https://static.zxtiku.com/wangke/imgs/topic/1ea08a79da7ec3b8361f2869c963996c.png"/>处可微，则函数在该点的两个偏导数<img src="https://static.zxtiku.com/wangke/imgs/topic/539e692e553553f4c5daf541ba7316a7.png"/>和<img src="https://static.zxtiku.com/wangke/imgs/topic/05653112c89d5e8a1afe702d63d2310c.png"/>都存在.