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: 36

Answer

$zw= 12(cos280^\circ+i\ sin280^\circ), \frac{z}{w}=\frac{1}{3}(cos240^\circ+i\ sin240^\circ)$

Work Step by Step

Given $z=2(cos80^\circ+i\ sin80^\circ)$ and $w=6(cos200^\circ+i\ sin200^\circ)$, we have: 1. $zw=12(cos(80+200)^\circ+i\ sin(80+200)^\circ)=12(cos280^\circ+i\ sin280^\circ)$ 2. $\frac{z}{w}=\frac{1}{3}(cos(80-200)^\circ+i\ sin(80-200)^\circ)=\frac{1}{3}(cos(-120)^\circ+i\ sin(-120)^\circ)=\frac{1}{3}(cos240^\circ+i\ sin240^\circ)$
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