Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Argument in complex numbers

  1. Mar 1, 2010 #1

    Mentallic

    User Avatar
    Homework Helper

    When given a complex number [itex]z=x+iy[/itex] and transforming this into its mod-arg form giving [itex]rcis\theta[/itex] where [itex]r=\sqrt{(x^2+y^2)}[/itex] and [itex]\theta=arctan(y/x)[/itex], we are assuming that [itex]-\pi/2<\theta<\pi/2[/itex].

    What if however a student is asked to convert the complex number -1-i into mod-arg form? If they just start to plug-and-chug they'll quickly end up with the result [itex]\theta=\pi/4[/itex] and all of a sudden they've changed the complex number into it's negative, 1+i.

    How does one avoid this dilemma?
     
  2. jcsd
  3. Mar 1, 2010 #2
  4. Mar 1, 2010 #3

    Mentallic

    User Avatar
    Homework Helper

    Thanks :smile:
     
  5. Mar 2, 2010 #4

    mathman

    User Avatar
    Science Advisor
    Gold Member

    Be careful with the angle domain. You have a semicircle, while it should be a full circle. The signs of x and y have to be taken into account so that you end up in the correct quadrant.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Argument in complex numbers
  1. Complex numbers (Replies: 2)

  2. Complex arguments (Replies: 2)

  3. Complex numbers (Replies: 2)

Loading...