# Help finding zeros of equation with trig function

1. Sep 6, 2014

### eHoaX

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

Last edited: Sep 6, 2014
2. Sep 6, 2014

### phinds

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.

3. Sep 6, 2014

### 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

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.

4. Sep 6, 2014

### Student100

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