如果具有二阶连续偏导数，则https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/00a66bfde04645bab10d1dc527f6eb6b.png
举一反三
- 设A=<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/bc546fc03fdb4ba3b7e6b144b6371d7f.png" />，B=Р(Р(A)) 下列（ ）表达式不成立。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/6e615703da60435893f9e9a9273e12e5.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/64c831067d054e71a6c76f43849d450d.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/72023a5250e44c12b98923044194f13d.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/c48e039a739c4502830eee7ae0ac1678.png" />
- 设 f 的导数连续， 是由 所围封闭曲面内侧，则https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/9a8faf24230c4485845bb5adabd15b5a.png
- 考虑二元函数在点处4条性质：（1）连续；（2）两个偏导数连续；（3）可微；（4）两个偏导数存在，则https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/567119e484564dc4beada6d8d80fb3c1.png
- 已知主视图和俯视图，下面左视图画法正确的有（ ）<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/2bcab5bbb4024d99b27781c7c286d861.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/c740df10c8d64a5c9f269c0808cfba30.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/d19031d8c17543f699d8827fa6ac1249.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/1780a38439af44618170b420943a6b6d.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/8b29c3cc4c2e4f3e919c5f22d4ac96f1.png" />
- 已知主视图和俯视图，下面左视图画法正确的有（ ）<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/0e67a6814bf3453d8a2560ad2803175b.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/9cbbab2efe124ef98699ab70b405efa7.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/43768386d66b41419559fe5bf0fb308d.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/3880af04e89d468c8c94acccd953d9c7.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/d4f57df49926458fba76fe114e40f01c.png" />