Differential Equations and Linear Algebra (4th Edition)

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

Chapter 1 - First-Order Differential Equations - 1.12 Chapter Review - Additional Problems - Page 111: 46

Answer

$y=e^{-\cos x}(x+1)$

Work Step by Step

We are given: $$\frac{dy}{dx}-(\sin x)y=e^{-\cos x}$$ Integrating factor is: $$I=e^{\int -\sin x dx}=e^{\cos x}$$ The equation becomes: $$\frac{d}{dx}(ye^{\cos x})=e^{-\cos x}e^{\cos x}=1$$ Integrating both sides: $$ye^{\cos x}=x+C$$ $C$ is an integration constant $$y=e^{-\cos x}(x+C)$$ We are given $y(0)=\frac{1}{e}$ $$e^{-1}=e^{\cos 0}C=e^{-1}C$$ $$\rightarrow C=1$$ The final solution is: $$y=e^{-\cos x}(x+1)$$
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