Re: [理工] [拉式] 98南交工數

看板Grad-ProbAsk作者ejialan (eji)時間12年前 (2012/02/14 14:17)推噓10(10推 0噓 3→)

留言13則, 10人參與討論串2/4 (看更多)

※ 引述《jerrysimon ()》之銘言： : http://0pics.com/images/image171.jpg

: 第18題，我原本想要直接分式，但發現很難做 : 然後我讓它等於2式相乘、使用摺積定理，但逆轉換後的摺積我不會做 : 請問有人知道這題該怎麼處理嗎? : 感謝~m(_ _)m~ Y(s) = 4/(s^2+1)^2/(s-1)^2 = (As+B)/(s^2+1)^2 + (Cs+D)/(s^2+1) + E/(s-1)^2 + F/(s-1) As+B = [Y*(s^2+1)^2] | s^2=-1 = [4/(s^2-2s+1)] | s^2=-1 = 4/(-2s) | s^2=-1 = 4s/(-2s^2) | s^2=-1 = 2s => A=2, B=0 [Y*(s^2+1)^2]_s | s^2=-1 (_s表示對s微分) = -8/(s-1)^3 | s^2=-1 = -8/(s^3-3s^2+3s-1) | s^2=-1 = -8/(-s+3+3s-1) = -4/(s+1) = -4(s-1)/(s^2-1) | s^2=-1 = 2s-2 = A + 2s * (Cs+D) | s^2=-1 = A + 2Ds -2C => D=1, C=2 E = [Y*(s-1)^2] | s=1 = 4/(s^2+1)^2 | s=1 = 1 F = [Y*(s-1)^2]_s | s=1 (_s表示對s微分) = -16s/(s^2+1)^3 | s=1 = -2 Y(s) = 2s/(s^2+1)^2 + 2s/(s^2+1) + 1/(s^2+1) + 1/(s-1)^2 -2/(s-1) y(t) = tsin(t) + 2cos(t) + sin(t) + te^t - 2e^t 答案選(A) -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 111.250.23.202

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squallting

02/14 14:20, , 1^F

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blazesunny

02/14 14:20, , 2^F

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a149851571

02/14 14:26, , 3^F

02/14 14:26, 3^F