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: 90

Answer

$$ - \frac{{\sqrt 3 }}{2} - \frac{1}{2}i$$

Work Step by Step

$$\eqalign{ & \frac{{2i}}{{ - 1 - i\sqrt 3 }} \cr & {\text{Convert the numerator and the denominator to trigonometric form}} \cr & 2i = 2\left( {\cos {{90}^ \circ } + i\sin {{90}^ \circ }} \right) \cr & - 1 - i\sqrt 3 = 2\left( {\cos {{240}^ \circ } + \sin {{240}^ \circ }} \right) \cr & {\text{Then,}} \cr & \frac{{2i}}{{ - 1 - i\sqrt 3 }} = \frac{{2\left( {\cos {{90}^ \circ } + i\sin {{90}^ \circ }} \right)}}{{2\left( {\cos {{240}^ \circ } + \sin {{240}^ \circ }} \right)}} \cr & {\text{Using the Quotient Theorem}} \cr & = \frac{2}{2}\left[ {\cos \left( {{{90}^ \circ } - {{240}^ \circ }} \right) + i\sin \left( {{{90}^ \circ } - {{240}^ \circ }} \right)} \right] \cr & {\text{Simplify}} \cr & = \cos \left( { - {{150}^ \circ }} \right) + i\sin \left( { - {{150}^ \circ }} \right) \cr & = \cos \left( {{{150}^ \circ }} \right) - i\sin \left( {{{150}^ \circ }} \right) \cr & {\text{Write in Rectangular form}} \cr & = - \frac{{\sqrt 3 }}{2} - i\left( {\frac{1}{2}} \right) \cr & = - \frac{{\sqrt 3 }}{2} - \frac{1}{2}i \cr} $$
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