How to use De Moivre's theorem to solve equations?

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Can someone please explain to me how to do question 1a? Thanks!

1 Answer
Mar 2, 2018

The solution is S={i}

Explanation:

We need

i^2=-1

The equation is

z^2+1=0

Therefore,

z^2+1+(color(red)(-1))=0+(color(red)(-1))

z^2+0=0+(color(red)(-1))=color(red)(-1)

z^2=color(red)(-1)

z^2=i^2

z=i