Complex Numbers (repost)

Question

Complex Numbers (repost)

+2

920

2

+501

My first post of this question is now not on the first page, so I thought I would repost it.

Find all possible integer values of $z$ such that the following system of equations has a solution for $z$ :

$\begin{align*} z^n &= 1, \\ \left(z + \frac{1}{z}\right)^n &= 1. \end{align*}$

Edit: $z$ can be a complex number, too!

Link to first question: https://web2.0calc.com/questions/help-plles

Davis Sep 7, 2019

2⁺⁰ Answers

0 Online Users

Rom · Answer 1 · 2019-09-08T07:20:25

$z = r e^{i \theta}\\ z^n = r^n e^{i n \theta}\\ z^n = 1 \Rightarrow r = 1\\ z = e^{i \theta}$

$z + \dfrac 1 z = e^{i\theta}+ e^{-i\theta} = 2\cos(\theta)\\~\\ \left(z + \dfrac 1 z \right)^n = 2^n \cos^n(\theta) = 1\\ \cos^n(\theta) = \dfrac{1}{2^n}\\ \cos(\theta) = \dfrac 1 2\\ \theta = \pm \dfrac{\pi}{3}$

$z = e^{\pm i \pi/3}$

.

Complex Numbers (repost)

0 users composing answers..

2⁺⁰ Answers

0 Online Users

Top Users

Sticky Topics

Complex Numbers (repost)

0 users composing answers..

2+0 Answers

0 Online Users

Top Users

Sticky Topics

2⁺⁰ Answers