曲线与x轴所围成的图形的面积可表示为（ ）https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/47164e270aee44e1bc292b7393cff903.png
举一反三
- x(t)的频谱为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/5bcfe4175fcb4fabbdb5f40d00b5343e.png"/>，则<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/45b1670ebd6245ff99cc376a8048a645.png" />的频谱为（ ） A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/09bc7326832a4a1fba983e74c6d85d35.png"/> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/95fca346a74e4a6cbba601cd6d9e26bf.png"/> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/6bf6b83111ad45efac7eb9a37a245c68.png"/> D: 其余选项都不对
- 历史曲线构件的图标是( )。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/dfb6b619f35547c590f6e6c6aab95b3f.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/e7e0aaa5f6e84ba89410cc93b06a451a.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/354425393230484ab64d64a718bd9bad.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/1f794e99ed004e3190fa5181c32fe4e8.png" />
- 图示各杆BC段为轴向拉伸（压缩）的是（ ） A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/412a1c88a2924281a60f66b253c86c67.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/7ef22ac8d02b49db8625a91064e510ef.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/23a086371806496786bdb9d1789a098d.png">
- 曲线的拐点为. （ ）https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/a9a518950e9b4b0d82e340179fd3392c.png
- 下列方程所描述的系统中（ ）是线性时不变系统。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/5740348e23d246eebda0442284882d6d.png"/> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/87c5df9c28f54b398bbedc5da45e7a02.png"/> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/ece1036e5a3c410e8f8b3de147910c04.png"/> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/69fc98a558ce4f3eb743c68be74cf923.png"/>