下图所示序列f(k)闭合表示式为http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/e3088842d7014311aa5241014415b8f3.bmp
举一反三
- 周期信号f(t)如下图所示，其直流分量为http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/bb02e5afe3fa474093913374442813ab.png
- 已知信号f(t)的波形如下图所示，则f(6-2t)的波形图为http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/414e4bc7b0b44f6e8f660e9dd1189014.bmp
- 图示结构C截面弯矩为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/4f75b4fba9ff4be1b04a5e100c86c65e.png" /> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/145877d7a442497f9fe1266fa394ba2e.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/1b6f8295e7bc44b0b8a2bee20e062fc4.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/18776e34a7504dfcbe40fbdf73958b14.png" /> D: 0
- 如主视图所示，三棱锥被截切，俯视图和左视图正确的是（ ）。 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/f6dde245be3a4ac286b637f07e1484fc.png"> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/04ae2221fc904cc1ac1caca4daaa8ab1.png"> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/e451d56ab1524240b603f2fa47aad33b.png"> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/0550413aeb5b436c88589bf8de2029af.png">
- 下列尺寸标注正确的是（ ） A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/79ed6f04ee2f415c917c9f280eccf07e.png"> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/4677ac7155c849bebe9d2ffd7458f4c4.png"> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/489ad68ff6294831bc43fa08990b59b7.png"> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201906/e829c514224942f1926c1823be08d3e7.png">