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Finding the period of a fxn

  1. Aug 24, 2008 #1
    x = (2/5)cos(t) + (1/5)sin(t)

    by graphing this, I found the period to be 2*pi.

    My concern is, when taking an exam I won't have time to bother with graphing or I'll get slammed with a weird graph and panic and get stuck.

    I'm pretty sure there is a way to find the period quickly with out graphing? I am running into this problem in my dyamical systems class and my calculus and trig are sooooooooo rusty.

    Thanks,
    Candio
     
  2. jcsd
  3. Aug 24, 2008 #2

    CompuChip

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    The function is made out of two parts, added together. What is the period of the first part? What is the period of the second part? What is the least common multiple of that (e.g. if the period for one is 3 and for the other one 4, then it will be 12; but if it is 3 and 6 then it will be 6).
     
  4. Aug 24, 2008 #3
    Ha! Thanks. You're the best :)

    lets see

    period 2/5.cos(t) = 2pi
    1/5.sin(t) = 2pi

    least common multiple = 2pi

    sweet
     
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