Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 8 - Polar Coordinates; Vectors - Section 8.3 The Complex Plane; De Moivre's Theorem - 8.3 Assess Your Understanding - Page 615: 39

Answer

$zw= 4\sqrt 2(cos15^\circ+i\ sin15^\circ), \frac{z}{w}= \sqrt 2(cos75^\circ+i\ sin75^\circ)$

Work Step by Step

Given $z=2+2i=2\sqrt 2(cos45^\circ+i\ sin45^\circ)$ and $w=\sqrt 3-i=2(cos330^\circ+i\ sin330^\circ)$, we have: 1. $zw=4\sqrt 2(cos(45^\circ+330^\circ)+i\ sin(45^\circ+330^\circ))=4\sqrt 2(cos15^\circ+i\ sin15^\circ)$ 2. $\frac{z}{w}=\sqrt 2(cos(45^\circ-330^\circ)+i\ sin(45^\circ-330^\circ))=\sqrt 2(cos(45^\circ+360^\circ-330^\circ)+i\ sin(45^\circ+360^\circ-330^\circ))=\sqrt 2(cos75^\circ+i\ sin75^\circ)$
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