以下哪个公式是周期性功率信号的功率谱密度公式（ ）
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 以下哪个公式是周期性功率信号的频谱公式（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/d866d2ef588941c592f11041e832b874.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/e96c211f3ae94824a5c743800a880c9a.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/31485515d551447dba1c8f91b27275f5.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/8f8844d055c2497fb4fde4750b229d7c.png">
- 下列方程为伯努利方程的是（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/0622f56257874ab19e680d587fd8a4fc.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/5ce3fc785b724e3da7d07b8d6a0ecaf3.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ab3de1c35e9e419fa301a33bddd5ee0c.png">+<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/2c226f2daecf40448b08c3b26a4db60e.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/88be95dd74814341a1894f32f073b9ec.png"><img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/00fbcbc7c3574f94934fa3adc8843ccf.png">
- 开环系统频率特性<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/d87c0f560f1542028a3602b52456fae0.png" />，当<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/c0f50539680f40a784c2a0d803f0f5d7.png" />时，其频率特性相角<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ff41a81bec7c421c8178de199c438e05.png" />（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/589b5e2ab46b459882a2824ff9567c36.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/370b677492de485ca61114324b5d00fe.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/95723a2a938f4944a98b18d89f607986.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/c08161009369424f9a3510d7c77d9943.png" />
- 以下哪个公式是能量信号的能量谱密度公式（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/812a671c7be94f8e904875cea2998b86.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ef8773972f3a42f4825e7e43103b588d.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/9028d577b3324e5d9b93feca76c25e82.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/90a3c17a5554452c8a3af089685dcf2d.png">
- 直线<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/64709df03a7b45ebbc6d752183b8f22e.png" />与直线<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/5ca5aa44859c42ddaa3207626d2b9537.png" />的公垂线方程为（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/a4c463fa2c3f49df9d7f2bb2e9fc4030.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/627b64a33e944efcba416aea0f40dc76.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/966e8a14e6754060b800dff88721784a.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/f8f41491de204a9eb3fb306208c3b08a.png" />