已知试利用此结果求下列积分:

A．V1投影轴平行倾斜线H投影面的投影，V1投影面上的投影反应倾斜线实长。 B．倾斜线一次换面换成投影面垂直线，二次换面换成投影面平行线求得倾斜线实长。 C．H1投影轴平行倾斜线V投影面的投影，H1投影面上的投影反应倾斜线实长。 D．直角三角形法求实长。

<img src='https://img2.soutiyun.com/ask/2020-12-10/976481945992252.png' />

如题图E3-19所示电路，已知<img src='https://img2.soutiyun.com/ask/2020-11-14/974193896718043.png' />试求电流i。 <img src='https://img2.soutiyun.com/ask/2020-11-14/974193908480716.png' />

已知<img src='https://img2.soutiyun.com/ask/2020-12-01/975701179868315.png' />,求对应的序列x(n). [利用级数展开式<img src='https://img2.soutiyun.com/ask/2020-12-01/975701192867058.png' />]

已知系统函数<img src='https://img2.soutiyun.com/ask/uploadfile/5421001-5424000/dd17f59cf10e3b21cdf550ec17506369.png' />，激励信号e(t)=e^-3tu(t)，试利用傅里叶分析法求响应r(t)。

已知微分方程 (x2+y)dx+f(x)dy=0 有积分因子μ=x，试求所有可能的函数f(x)．

<img src='https://img2.soutiyun.com/ask/2020-12-28/977993945514249.jpg' /> <img src='https://img2.soutiyun.com/ask/2020-12-28/977993961306152.jpg' /> <img src='https://img2.soutiyun.com/ask/2020-12-28/977994003441562.jpg' />

<img src='https://img2.soutiyun.com/ask/2020-10-07/970909112927228.png' /> <img src='https://img2.soutiyun.com/ask/2020-10-07/970909120631669.png' /> <img src='https://img2.soutiyun.com/ask/2020-10-07/970909128253105.png' />

已知<img src='https://img2.soutiyun.com/ask/2020-12-21/977394789222571.png' />试求内积<img src='https://img2.soutiyun.com/ask/2020-12-21/977394803059362.png' />

<img src='https://img2.soutiyun.com/ask/2020-12-16/976966197588706.jpg' /> <img src='https://img2.soutiyun.com/ask/2020-12-16/976966214011646.jpg' />

已知有限长序列x(n)(0≤n≤N-1)的DFT为X(k)，试利用X(k)导出下列各序列的DFT。 <img src='https://img2.soutiyun.com/ask/2021-01-29/980777730400856.png' />

给定求积节点x₀=1/4,x₁=3/4,试推出计算积分<img src='https://img2.soutiyun.com/ask/2020-09-09/968515466075717.png' />的插值型求积公式,并写出它的截断误差.

<img src='https://img2.soutiyun.com/ask/2020-10-20/972042931928302.png' />

<img src='https://img2.soutiyun.com/ask/2020-11-02/973173912091949.png' />

<img src='https://img2.soutiyun.com/ask/2020-07-10/963220678048646.png' />

是 否