下列积分中等于零的是
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 如图所示电路的逻辑表达式F=（ ）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/8655693a417e4e43a32e0732ed533c96.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/beda73211aea49f082d9137fd4eb0526.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7388c99ee0824f20bcf85893934a2f6a.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/9a5c81e78b344c79a9389e932a7f55ce.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/82193a9a030243728012b02e15718987.png" />
- 下列各表达式正确的是（）。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/c00e74606aff46b3bd686c1cbb405da6.gif" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/a9452605ec5b4dfc8fede5ae6baae903.gif" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/316677d9b4fe41d09b0ef5f8b18e4a0b.gif" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1d4a5808f5524820897bf23dd439ad0c.gif" />
- 下列命名正确的是( ) A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/45d758d675564df2b279142c14ae9e2e.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/4889492bf6634f04b7c4e5c944f66ed8.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/70bc128530144f07aa006af0ebe6a989.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/ddcdceddcb9a49bf8ab24aea015a7a9a.png">
- 下列哪些函数是调和函数？( ) A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/30a8b864644b4f27953e4f399dc4d71c.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/96069e2a68cd483195966ca8c29148cf.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/4182d5dc35bd4c61a1d6d7770aeb455f.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/a862359c882e445498961560101f6776.png" />
- 如图示并联管路，已知各支路的沿程阻力系数之比为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/6e209020d20f4543823ce6516ae8ca06.png" />，管长之比为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/50814fe028094040bc955d8e1542b6d2.png" />，且<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/40b4c6a9565b483590c5c7d607e7ed66.png" />，则两支管的流量之比<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1055534bfce6426a94682ba086a5b17e.png" />=（）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/77815369f5cd41f3a2e68b9524b454c5.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/0cd231eebe45465f941a0f614743e6d2.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7555afa5223e40bf89ca575cf7b52754.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/1b06cd474b844644a6d97ad87d208e94.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/d0b2bca045414236a7d1c9925a9264f2.png" />