1. Limited time only! Sign up for a free 30min personal 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!

Finding the period of trig series analytically?

  1. Sep 3, 2011 #1
    Is there a way to calculate the period of a trigonometric series (like the one below) analytically?

  2. jcsd
  3. Sep 3, 2011 #2


    User Avatar
    Science Advisor

    The period in this case can be gotten from: 8t = 2π or t = π/4. This works since the other term has a period 16t = 2π or t = π/8 which is a harmonic.
  4. Sep 3, 2011 #3
    Sorry, I'm still confused. For this example...


    ...I have graphed this in MATLAB, and graphically found a period of about 2.1. I am trying to apply what you suggested, but can't figure out how to calculate the period of 2.1...

    Attached Files:

    • ex.png
      File size:
      28.6 KB
  5. Sep 3, 2011 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The sum of two periodic functions will be periodic it the two periods are commensurable. That means the ratio of their periods is a rational number. And in that case, the period is the least common multiple of the individual periods. For non-integers p and q, the LCM is the least number z such that ap = z and bq = z for a and b integers.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook