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Homework Help: Polar form

  1. Mar 14, 2010 #1
    1. The problem statement, all variables and given/known data
    solve below using de Moivre's theorem, in polar form
    z^3 = i

    2. Relevant equations
    r CIS theta

    Answer:CIS pi/6, CIS 5pi/6, CIS (-pi/6)

    3. The attempt at a solution
    r^3 = sqrt(0^2+1^2)
    r^3 = sqrt (1)
    r = sqrt (1)

    no idea how to get the angle
  2. jcsd
  3. Mar 14, 2010 #2


    User Avatar
    Gold Member

    It is not true that i = 1, which is essentially what you have done in solving the equation. 1 is simply the modulus of the complex number i.

    Try writing the complex number i in polar form i.e. in the form [tex]R cis \theta[/tex], and then taking the cube root of both sides of the equation.
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