Complex number

$\hspace{-16}\textbf{(1)\;Solve the equation z^4=\bar{z}}:$\\\\ $\textbf{(2)\;If Z\in\mathbb{C}\textbf{\;and $\mid z\mid<\frac{1}{2}.$ Then Show that }}$\\\\ \mathbf{\mid (1+i).z^3+iz\mid<\frac{3}{4} }

4 Answers

106
Asish Mahapatra ·

z=eiθ

=> e4iθ = e-iθ

=> cos(4θ) = cosθ and sin(4θ) = sin(π+θ)

=> 4θ = 2nπ ± θ and 4θ = nπ + (-1)n(π+θ)

=> 4θ = 2nπ-θ
=> θ=2nπ/5

341
Hari Shankar ·

you missed z=0. Which is why you must write out why you assumed z=e1θ.

21
Arnab Kundu ·

/z/ =0 or 1, when /z/ = 1, z is fifth root of unity, when /z/ =0 , z=0 :)

106
Asish Mahapatra ·

oh yeah ... missed it

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