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Complex numbers root problems

  1. Sep 4, 2011 #1
    1. The problem statement, all variables and given/known data
    What is the square root of z=-9

    2. Relevant equations

    3. The attempt at a solution
    Is it possible of me to not use De'Moivre's theorem to solve this question??
    Solution :
    z= [itex]\sqrt{-9}[/itex]
    z=[itex]\sqrt{9}[/itex] x [itex]\sqrt{}-1[/itex]
    z=[itex]\pm3[/itex] i

    Will this method be acceptable?? Is this still under the topic complex roots?
  2. jcsd
  3. Sep 5, 2011 #2


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