Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 8 - Complex Numbers, Polar Equations, and Parametric Equations - Section 8.2 Trigonometric (Polar) Form of Complex Numbers - 8.2 Exercises - Page 364: 29

Answer

$-2-2i\sqrt 3$

Work Step by Step

$\cos 240^{\circ}=-0.5$ and $\sin 240^{\circ}=-\frac{\sqrt 3}{2}$ Substituting these values in the question, $4(\cos 240^{\circ}+i\sin 240^{\circ})=4(-0.5+i(-\frac{\sqrt 3}{2}))=-2-2i\sqrt 3$
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