Differential Equations and Linear Algebra (4th Edition)

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

Appendix A - Review of Complex Numbers - Exercises for A - Problems - Page 796: 19

Answer

$x^{2-i}=x^2\cos(\ln x)+i[-x^2\sin (\ln x)]$

Work Step by Step

We will use the Euler's formula \[e^{i\theta}=\cos \theta+i\sin\theta\] $x^{2-i}=x^2x^{-i}$ $x^{2-i}=x^2e^{-i\ln x}$ $x^{2-i}=x^2e^{i(-\ln x)}$ By using Euler's Formula $x^{2-i}=x^2\left[\cos(-\ln x)+i\sin (-\ln x)\right]$ $x^{2-i}=x^2\left[\cos(\ln x)-i\sin (\ln x)\right]$ $x^{2-i}=x^2\cos(\ln x)+i[-x^2\sin (\ln x)]$ Here $\;u(x)=x^2\cos(\ln x)$ and $v(x)=-x^2\sin (\ln x)$ Hence $\;\;x^{2-i}=x^2\cos(\ln x)+i[-x^2\sin (\ln x)]$.
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