设，则 （ ）https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/b9bc88c9887a460d9644f58aa52a54a3.png
举一反三
- 设，则（ ）https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/65a0d3434521400ea3cfef4ee4ce833f.png
- 设，则（ ）https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/3b5592af1a9946d0860bae2263bcaddd.png
- 设，且，则（ ）https://image.zhihuishu.com/zhs/onlineexam/ueditor/201911/54eb7bb314af4d48acd79bdaed0a3a54.png
- 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
- 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">