Re: [理工] [工數]Laplace
※ 引述《jay0748 (山豬)》之銘言：
: 題目
: f(t)=u(t-2π)e^(t-2π) cost
: 求 L{f(t)}
: 請幫忙解答 謝謝
法一
f(t)=u(t-2π)e^(t-2π) cost
=u(t-2π)e^(t-2π) cos(t-2π+2π)
F(s)=e^(-2πs)L[e^tcos(t+2π)]
=e^(-2πs)L[cos(t)]s=s-1
=e^(-2πs)(s-1)/((s-1)^2+1)
法二
f(t)=u(t-2π)e^(t-2π) cost
F(s)=L[u(t-2π)e^(t-2π) cost]
=e^(-2π)[ L[u(t-2π)cos(t-2π+2π)] ]s=s-1
=e^(-2π)[e^(-2πs)/s^2+1]s=s-1
=e^(-2π)e^(-2π(s-1))(s-1)/((s-1)^2+1)
=e^(-2πs)(s-1)/((s-1)^2+1)
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◆ From: 140.118.233.115
※ 編輯: Tall781218 來自: 140.118.233.115 (08/17 18:59)
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08/17 18:50, , 1F
08/17 18:50, 1F
※ 編輯: Tall781218 來自: 140.118.233.115 (08/17 19:01)
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7年前
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