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Help finding zeros of equation with trig function

  1. Sep 6, 2014 #1
    1. The problem statement, all variables and given/known data

    I need to find the times when the velocity is 0.
    I am having difficulties finding multiple values for t.

    v(t)=0

    2. Relevant equations

    v(t)=-40/3*cos(3/2*t)-5.129

    3. The attempt at a solution
    Attempt at solution:

    v(t)=-40/3*cos(3/2*t)-5.129

    V(t)=0

    0=-40/3*cos(3/2*t)-5.129

    cos(3/2*t)=-5.129*3/40

    3/2*t=arccos(-5.129*3/40)

    t=2/3*arccos(-5.129*3/40)

    t=1.31

    now I am not able to find the other values of t, I tried adding pi/2 but it didn't work

    (it should be in radians)
     
    Last edited: Sep 6, 2014
  2. jcsd
  3. Sep 6, 2014 #2

    phinds

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    Gold Member
    2016 Award

    Just as a suggestoin, "help" is not a subject line that is going to draw people who have an interest in the particular KIND of help you need.

    Also, you need to read the forum rules. There's a template you should be using for homework problems.
     
  4. Sep 6, 2014 #3

    gneill

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    Staff: Mentor

    Hi eHoaX. Welcome to Physics Forums.

    As phinds mentioned, use the posting template provided when you begin a new thread in the homework sections. Also choose an threat title that describes the subject matter of your question; "Help" does not describe the topic or content, and one-word titles are almost never descriptive and are disallowed in general.

    I will change the thread title to: Help finding zeros of equation with trig function.

    I have also deleted your duplicate of this thread (which had no responses yet), although the title was much better :smile:

    See the posting guidelines in the pinned thread, "Guidelines for students and helpers", at the top of the list of threads in the homework sections.
     
  5. Sep 6, 2014 #4

    Student100

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    Education Advisor
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    Have you tried -2pin and + 2pin, there should be infinite times when velocity is zero.
     
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