Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 8 - Application of Trigonometry - 8.5 Trigonometric (Polar) Form of Complex Numbers: Products and Quotients - 8.5 Exercises - Page 802: 89

Answer

$$2\sqrt 3 - 2i$$

Work Step by Step

$$\eqalign{ & \frac{8}{{\sqrt 3 + i}} \cr & {\text{Convert the numerator and the denominator to trigonometric form}} \cr & 8 = 8\left( {\cos {0^ \circ } + i\sin {0^ \circ }} \right) \cr & \sqrt 3 + i = 2\left( {\cos {{30}^ \circ } + \sin {{30}^ \circ }} \right) \cr & {\text{Then,}} \cr & \frac{8}{{\sqrt 3 + i}} = \frac{{8\left( {\cos {0^ \circ } + i\sin {0^ \circ }} \right)}}{{2\left( {\cos {{30}^ \circ } + \sin {{30}^ \circ }} \right)}} \cr & {\text{Using the Quotient Theorem}} \cr & = \frac{8}{2}\left[ {\cos \left( {{0^ \circ } - {{30}^ \circ }} \right) + i\sin \left( {{0^ \circ } - {{30}^ \circ }} \right)} \right] \cr & {\text{Simplify}} \cr & = 4\left[ {\cos \left( { - {{30}^ \circ }} \right) + i\sin \left( { - {{30}^ \circ }} \right)} \right] \cr & = 4\left[ {\cos \left( {{{30}^ \circ }} \right) - i\sin \left( {{{30}^ \circ }} \right)} \right] \cr & {\text{Write in Rectangular form}} \cr & = 4\left[ {\frac{{\sqrt 3 }}{2} - i\left( {\frac{1}{2}} \right)} \right] \cr & = 2\sqrt 3 - 2i \cr} $$
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