1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How do you find the radial value?

  1. Apr 19, 2007 #1
    What is the radial value for the 3rd root of the complex number 4 + -2i ?
     
  2. jcsd
  3. Apr 19, 2007 #2

    J77

    User Avatar

    Did they teach you Euler's formula and De Moivre?
     
  4. Apr 19, 2007 #3
    De Moivre's Theorem
     
  5. Apr 19, 2007 #4

    J77

    User Avatar

    So, you know how to write the complex number in exponential form?
     
  6. Apr 19, 2007 #5
    Can you refresh my memory please?
     
  7. Apr 19, 2007 #6

    J77

    User Avatar

    Euler says that a complex number can be written as [tex]z=re^{i\phi}[/tex], where r is the absolute value of z.

    What is r in your case?
     
  8. Apr 19, 2007 #7
    r = 2 square root of 5?
     
  9. Apr 19, 2007 #8

    J77

    User Avatar

    Yep -- [tex]\sqrt{20}[/tex]. So what's the 3rd root of r?
     
  10. Apr 19, 2007 #9
    that's where im stuck. how do you do that?
     
  11. Apr 19, 2007 #10

    J77

    User Avatar

    De Moivre: [tex]z^n=(re^{i\phi})^n=r^ne^{in\phi}[/tex]
     
  12. Apr 19, 2007 #11
    i'm lost...=/
     
  13. Apr 19, 2007 #12

    J77

    User Avatar

    For the 3rd root, what's n in my previous post?
     
  14. Apr 19, 2007 #13
    it's 3 right?
     
  15. Apr 19, 2007 #14

    J77

    User Avatar

    Nope -- what's a sqaure root expressed as a power?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?