采用负反馈连接时，如前向通道的传递函数为G(s)，反馈通道的传递函数为H(s)，则其等效传递函数为 ( ) A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/22c0346d04a34aa9926531e2d3dd47de.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/0e078cd10d7b42a399c9830856166423.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/1b1c0e6431754e20937fadb80e5a9d08.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/1805bdfbfb754c8988c33982100137fe.png" />

以下列4个信号的拉普拉斯变换，不存在傅里叶变换的是( ) A: 1 B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202106/8851fc1d1d25423f99532d86a4ab00fc.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202106/0aebd05182244a7692c57e132a11aeeb.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202106/2c0c1185c38e4c119d3827ce6d608550.png" />

一阶系统的时间常数为T，其单位斜坡响应为（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/67e3c0d52e254647b240f082770206ce.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/77cbfaa7e7c347c9a502d35f1a8b3f5c.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/52b5ceec9ed54c339da07e37bc70083e.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/698f17a321984af99eeee8732000c80d.png" />

已知单边拉普拉斯变换<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202101/880fd350069743a4a2d3750ba3a7e5df.png" />，则对应原函数的终值<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202101/85c3dd75650d4b01bbbb307f9a828b67.png" />=（ ）。 A: 4 B: 3 C: 2 D: 1

双纽线<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/ac4dfd0de9744513843c41341938f31c.png" />所围成的区域面积可用定积分表示为（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/b3a266adc8704187b18601cd19efc069.png" /> <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/fbc5959fd78d4d09ae216f05e45741c0.png" />. <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/02b5a6e0e400485382b137795ebb9ef1.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/45fb209600124a569d31e4c0ed4264f9.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202102/d5291bc308bc4880919d6f34ce4f7539.png" />