Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 8 - Section 8.3 - Polar Form of Complex Numbers; De Moivre's Theorem - 8.3 Exercises - Page 611: 93

Answer

$z=\frac{1+\sqrt 5}{2}i$ $z=\frac{1-\sqrt 5}{2}i$

Work Step by Step

$z^2-iz+1=0~~$ ($a=1,b=-i,c=1$): $z=\frac{-b±\sqrt {b^2-4ac}}{2a}=\frac{-(-i)±\sqrt {(-i)^2-4(1)(1)}}{2(1)}=\frac{i±\sqrt {-5}}{2}=\frac{i±\sqrt 5i}{2}$ $z=\frac{1+\sqrt 5}{2}i$ or $z=\frac{1-\sqrt 5}{2}i$
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