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Math Help - complex numbers in polar form

  1. #1
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    complex numbers in polar form

    if z=5i and w=(-9*sqrt(2))/2 + (9*sqrt(2))/2

    determine z/w in polar form

    Could some one please get me started I dont know how you can find the angle formed when z=5i?
    dont I need a real part not just imaginary

    Thanks
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  2. #2
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    Hello,

    Quote Originally Posted by samdmansam View Post
    if z=5i and w=(-9*sqrt(2))/2 + (9*sqrt(2))/2
    Isn't it w=(-9*sqrt(2))/2 + (9*sqrt(2))/2 i ?

    determine z/w in polar form
    First of all, multiply above and below by the conjugate of w

    Could some one please get me started I dont know how you can find the angle formed when z=5i?
    I think this would come later
    Try to get to the step I mentioned.

    dont I need a real part not just imaginary
    If you have z=5i, it means that z=0+5i

    |z|=5

    5i=5(\cos(\theta)+i \sin(\theta)

    So we can see that \cos(\theta)=0 and \sin(\theta)=1
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  3. #3
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    there is a similar question asked previously have a look:
    http://www.mathhelpforum.com/math-he...-form-c-n.html
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  4. #4
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    thanks but need a bit more help

    I got (5/9)cis(11/6*pi)
    but the answer needs to be between (-pi,pi]?
    dont really understand that
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