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!

Series Question

  1. Sep 21, 2007 #1
    1. The problem statement, all variables and given/known data

    Hello, I am wondering if someone can help with the following. I am supposed to show that

    Series from n = 1 to inf r^n*cos(nx) = rcosx -r^2/(1-2*rcosx + r^2). I am supposed to relate it to the fact that z = rexp(ix). I know that this expression is the real part of z^n or r^n*exp(inx). But I'm not sure what to do after that?

    Any hints would be greatly welcome! Thanks!!!

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 21, 2007 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Written in exponential form it's a geometric series. Sum it.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Series Question
  1. Series question (Replies: 2)

  2. Series Question (Replies: 8)

  3. Series Question (Replies: 1)

  4. Series Question (Replies: 2)

  5. A series question (Replies: 4)

Loading...