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 - 1.6 First-Order Linear Differential Equations - Problems - Page 59: 17

Answer

$y=2\sin x\ln \sin x+2\sin x$

Work Step by Step

We are given: $(\sin x)y'-y\cos x=\sin 2x$ $(\sin x)y'-y\cos x=2\sin x \cos x$ Divide both sides by $\sin x$ $\frac{dy}{dx}-y\cot x=2 \cos x$ Integrating factor: $I(t)=e^{\int -\cot xdx}dt=e^{-\ln \sin x}=\frac{1}{\sin x}=\csc x$ Multiply both sides by the intergrating factor: $\csc x\frac{dy}{dx}-y\csc x\cot x=2 \csc x\cos x$ $\frac{d}{dx}(y \csc x)=2\cot x$ Integrate both sides: $y \csc x=2\ln \sin x+c$ $y=2\sin x\ln \sin x+c\sin x$ Since $y(\frac{\pi}{2})=2$ $2=2\sin (\frac{\pi}{2})\ln \sin (\frac{\pi}{2})+c\sin (\frac{\pi}{2})$ Solve for $c$: $c=2$ Hence general solution is $y=2\sin x\ln \sin x+2\sin x$
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