Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 8 - Section 8.3 - Products and Quotients in Trigonometric Form - 8.3 Problem Set - Page 440: 64

Answer

$\frac{\sqrt 3}{4}-\frac{1}{4}i$

Work Step by Step

$\sqrt {3}+i$ in trigonometric form is $2(\cos 30^{\circ}+i\sin 30^{\circ})$ We use de Moivre's theorem to find its reciprocal. $(\sqrt {3}+i)^{-1}=[2(\cos30^{\circ}+i\sin30^{\circ})]^{-1}$ $=(2)^{-1}[\cos(-1\cdot 30^{\circ})+i\sin(-1\cdot30^{\circ})]$ $=\frac{1}{2}(\cos -30^{\circ}+i\sin-30^{\circ})$ In standard form, our result is $\frac{1}{2}(\frac{\sqrt {3}}{2}+i\cdot -\frac{1}{2})=\frac{\sqrt 3}{4}-\frac{1}{4}i$
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