Elementary Differential Equations and Boundary Value Problems 9th Edition

Published by Wiley
ISBN 10: 0-47038-334-8
ISBN 13: 978-0-47038-334-6

Chapter 6 - The Laplace Transform - 6.2 Solutions of Initial Value Problems - Problems - Page 320: 10

Answer

$2e^{-t} \cos 3t-\dfrac{5}{3}e^{-t} \sin 3t$

Work Step by Step

Since, $\mathcal{L}(e^{at} \cos bt)=\dfrac{s-a}{(s-a)^2+b^2}$ and $\mathcal{L}(e^{at} \sin bt)=\dfrac{b}{(s-a)^2+b^2}$ Here, we have $F(S)=\dfrac{2s-3}{s^2+2s+10}$ or, $= \dfrac{2s+2-5}{s^2+2s+10}$ or, $=2 [\dfrac{s+1}{(s+1)^2+(3)^2}]-\dfrac{5}{3} [\dfrac{3}{(s+1)^2+(3)^2}] $ or, $=\mathcal{L}(2e^{-t} \cos 3t-\dfrac{5}{3}e^{-t} \sin 3t)$ Therefore, the required inverse Laplace transform is: $\mathcal{L}^{-1}[\mathcal{L}(2e^{-t} \cos 3t-\dfrac{5}{3}e^{-t} \sin 3t)]=2e^{-t} \cos 3t-\dfrac{5}{3}e^{-t} \sin 3t$
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