Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 9 - Polar Coordinates; Vectors - Chapter Review - Review Exercises - Page 635: 20

Answer

$zw=6(\cos(2\pi)+i\sin{(2\pi}))$ and $\frac{z}{w}=\frac{3}{2}(\cos({\frac{8\pi}{5})}+i\sin{\frac{8\pi}{5}})$.

Work Step by Step

We know that if $z=a(\cos{\alpha}+i\sin{\alpha})$ and $w=b(\cos{\beta}+i\sin{\beta})$, then $zw=ab(\cos({\alpha+\beta)}+i\sin{(\alpha+\beta})$ and $\frac{z}{w}=\frac{a}{b}(\cos({\alpha-\beta)}+i\sin{(\alpha-\beta})$. Hence here: $zw=(3)(2)(\cos({\frac{9\pi}{5}+\frac{\pi}{5})}+i\sin{(\frac{9\pi}{5}+\frac{\pi}{5}}))\\zw=6(\cos(2\pi)+i\sin{(2\pi}))$ and $\frac{z}{w}=\frac{1}{1}(\cos({\frac{9\pi}{5}-\frac{\pi}{5}))}+i\sin{(\frac{9\pi}{5}-\frac{\pi}{5}}))\\\frac{z}{w}=\frac{3}{2}(\cos({\frac{8\pi}{5})}+i\sin{\frac{8\pi}{5}})$.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.