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

Partial sum of geometric series

  1. Jun 6, 2009 #1
    ok so i know how to calculate the partial sum of a geometric series.

    But lets say i only want to calculate the sum of every other term, how would i do this?

    example:

    .5^0+.5^1+.5^2+...+.5^n = (.5^(n+1) - 1)/(.5-1)

    but what equation can i use to get the sum of only these terms:

    .5^1+.5^3+.5^5...+.5^n where n is odd
     
  2. jcsd
  3. Jun 6, 2009 #2

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Hint:

    See if you can re-write it as another geometric series, utilizing that an odd number n=2m+1, for m integer.
     
  4. Jun 6, 2009 #3
    yea i actually need to do it for the even ones for my equation haha

    ok so i think i got it, not going to write it all out because i;m busy, but thank you :)
     
  5. Jun 6, 2009 #4

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    And, of course, (.5)n, for n, even, n= 2m, is (.25)m so you have just another geometric series.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Partial sum of geometric series
  1. Geometric Series (Replies: 2)

Loading...