Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 8 - Linear Differential Equations of Order n - 8.3 The Method of Undetermined Coefficients: Annihilators - Problems - Page 525: 38

Answer

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Work Step by Step

The general solution for the given differential equation is: $y(x)=c_1\cos wt+c_2 \sin wt+A_0\cos wt+B_0\sin wt$ The trial solution for $y_p=A_0\cos x+B_0\sin x$ can be computed as by plugging back into the given differential equation. So, we have: $(D^2+w^2)y_p(x)= \frac{F_0}{m}\cos wt \\ (D^2+w^2)(A_0\cos wt+B_0\sin wt)=\frac{F_0}{m}\cos wt \\2B_0w=\frac{F_0}{m}$ On comparing coefficients, we get: $B_0=\frac{F_0}{2mw}$ Therefore, the general solution for the given differential equation is: $y(x)=c_1\cos wt+c_2\sin wt+\frac{F_0}{2mw} \sin wt$ Given $y(0)=1\\y'(0)=0$ Substitute $c_1=1\\ wc_2=0$ Then we have $c_1=1\\ c_2=0$ Hence, $y=\cos wt+\frac{F_0}{2mw}\sin wt$
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