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How to solve 4/3 sin(x) = x

  1. May 4, 2009 #1
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    those above steps imo are unnecessary, all i need to know is how to solve 4/3(sin theta)=theta, thanks in advance!
     
  2. jcsd
  3. May 4, 2009 #2

    Mark44

    Staff: Mentor

    Re: trig

    Two things:
    1. Is your equation 4/3 * sin(theta) = theta or is it 4/[3 sin(theta)] = theta?
    2. You are not going to be able to solve your equation, whichever one it is, by algebraic means. The best you can do is to get an approximate solution.
     
  4. May 4, 2009 #3
  5. May 4, 2009 #4

    Mark44

    Staff: Mentor

    Re: trig

    The link you gave is broken, so I don't know what you meant to show me. In any case, what I said in post 2 still applies.
     
  6. May 4, 2009 #5
    Re: trig

    its not broken, all you have to do is click on the address bar and press enter, as if you were typing the url in.
     
  7. May 4, 2009 #6

    diazona

    User Avatar
    Homework Helper

    Re: trig

    choob is actually right, you have to do something like copying and pasting the URL instead of just following the link. The site is probably trying to prevent direct linking.

    Anyway, the PDF file doesn't change anything - there is no analytic solution. You would need to use a graphing calculator or a computer to find the answer. (There's probably some sort of series expansion trick or something you could use to get a good approximation by hand)
     
  8. May 5, 2009 #7

    Cyosis

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    Homework Helper

    Re: trig

    If it's 4/3 * sin(theta) = theta you can find one pretty obvious solution.
     
    Last edited: May 5, 2009
  9. Jun 18, 2009 #8
    Re: trig

    freeexampapers has had a lot of bandwidth problems. We welcome direct linking and plan to have enough bandwidth to allow this.
     
  10. Jun 18, 2009 #9
    Re: trig

    Hi Cyosis ! I took some time looking and pondering of the possible solution and i could not figure it out , I hope you can provide me of the partial solution. Thank you.
     
  11. Jun 18, 2009 #10
    Re: trig

    Can somebody explain what's the task?
     
  12. Jun 18, 2009 #11
    Re: trig

    solve for theta
     
  13. Jun 18, 2009 #12
    Re: trig

    i tried using maclaurin's series and i manage to work out with the answer of 1.28 but i guess it is rather tedious.
     
  14. Jun 18, 2009 #13

    rock.freak667

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    Homework Helper

    Re: trig

    Well you could use the Newton-Raphson iterative method and find an approximation.
     
  15. Jun 18, 2009 #14
    Re: trig

    Yes indeed Newton Raphson method can solve and it is similar to taylor'series.
    Is there any other method to solve this question algebraically?
     
    Last edited: Jun 19, 2009
  16. Jun 19, 2009 #15

    Mentallic

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    Homework Helper

    Re: trig

    No.
    Yes, I was also quite dissappointed to hear that such a simple result such as the one you have presented has no means of being algebraically solved; but what can you do...
     
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