作者a016258 (失去羽翼的羊)
看板Grad-ProbAsk
标题Re: [问题] 工数
时间Fri Apr 10 09:26:36 2009
※ 引述《Secertman (独在异乡为异客)》之铭言：
: ※ 引述《ICRO (圣文大色胚)》之铭言：
: : y"+9y=tcost
个人觉得 用逆运子还是最快...
( D^2 + 9 )y = tcost
yh = c1 * cos3t + c2 * sin3t
1 it it 1
yp = Re ---------- te = Re[ e ----------- t ]
D^2 + 9 (D+i)^2 + 9
it 1 it 1 1
= Re [ e -------------- t ] = Re [ e * --- * ----------------------- t ]
D^2 +2iD + 8 8 1- (-iD/4 - D^2 / 8 )
it 1 i
= Re [ e * ------ * ( t - ----- ) ]
8 4
= Re [ ( cost + isint ) * ( t - i/4 ) * 1/8 ]
tcost sint
= ----- + ------
8 32
=> y = yh + yp
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 140.114.198.110
1F：→ Secertman:嗯嗯 这样比较快 04/10 09:36
2F：推 Aaron1025:跟我一样算法 前面推文有讲~ 04/10 11:29