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: 37

Answer

$zw=4(cos\frac{9\pi}{40}+i\ sin\frac{9\pi}{40}), \frac{z}{w}=cos\frac{\pi}{40}+i\ sin\frac{\pi}{40}$

Work Step by Step

Given $z=2(cos\frac{\pi}{8}+i\ sin\frac{\pi}{8})$ and $w=2(cos\frac{\pi}{10}+i\ sin\frac{\pi}{10})$, we have: 1. $zw=4(cos(\frac{\pi}{8}+\frac{\pi}{10})+i\ sin(\frac{\pi}{8}+\frac{\pi}{10}))=4(cos\frac{9\pi}{40}+i\ sin\frac{9\pi}{40})$ 2. $\frac{z}{w}=cos(\frac{\pi}{8}-\frac{\pi}{10})+i\ sin(\frac{\pi}{8}-\frac{\pi}{10})=cos\frac{\pi}{40}+i\ sin\frac{\pi}{40}$
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