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Math Help - Discrete fourier transform

  1. #1
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    Discrete fourier transform

    what does DFT achieve?
    Last edited by retroscience; November 11th 2010 at 11:37 AM.
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  2. #2
    MHF Contributor Bruno J.'s Avatar
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    I suggest instead that you post an attempted solution and that we help you track your mistakes if you make any.
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  3. #3
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    ok
    Last edited by retroscience; November 11th 2010 at 11:38 AM.
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  4. #4
    MHF Contributor Bruno J.'s Avatar
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    Quote Originally Posted by retroscience View Post
    but i just dont have the time to type out my 4 pages of math during revision time.
    I don't see why a stranger on the internet should be more inclined to do this for you than you should be to do it for yourself.
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  5. #5
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    no problem
    Last edited by retroscience; November 11th 2010 at 11:38 AM.
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  6. #6
    MHF Contributor Bruno J.'s Avatar
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    If you had read the sticky thread in the Analysis forum, called "List of rules used to moderate MHF - please read carefully before posting.", you would have found :

    11. Show some effort. If you want help with a question it is expected that you will show some effort. Effort might include showing your working, taking the time to learn how to typeset equations using latex (there is an entire subforum devoted to this), formatting your question so that it is more easily understood, using effective post titles and posting in the appropriate subforum, making a genuine attempt to understand the help that is given before asking for more help and learning from previous questions asked. Moderators reserve the right to Close threads in cases where the member is not making a genuine effort (particularly if the member is spamming the forums with multiple questions of exactly the same type). It should also be remembered that all contributors to MHF are unpaid volunteers and are under no obligation to answer a question.
    As the name suggests, a "help" forum is for help.
    Would you go see your professor during his office hours to ask him to do the problem for you? I bet not.

    I'm done in this thread. Good luck anyways and please take no offense, I'm only here to help.
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  7. #7
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    ok
    Last edited by retroscience; November 11th 2010 at 11:39 AM.
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  8. #8
    MHF Contributor Bruno J.'s Avatar
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    Quote Originally Posted by retroscience View Post
    ok, are you happy now that you have embarassed someone who isnt as good at math as you.
    sorry that i ever came to this forum.
    you by your own choice and will decided to open this post and criticise.i didnt spam you or anyone telling them to help.

    thanks alot.
    thats really helped my confidence.
    you know some of us are biologists who havent done math in 10yrs, we r not lazy or stupid as you have jumped to conclusions.

    just to let you know you've made me feel like **** n i havent even done anything wrong.

    thanks a lot.
    I did not criticize you for anything other than your manners. I especially did not criticize your math, as I never got to see any kind of sample of it.

    My first post in this thread was an offer to help you if you'd just attempt some kind of solution, using whatever material you have at hand. The idea is that I can see what you are having trouble with and give you specific, personalized help, for free. What more could you ask for? If you want a general course on the DFT, you'll find a bunch of PDFs online, many of them I'm sure containing examples.

    If you go see your professor for help, and you tell him/her "I don't understand the DFT", the first question you'll get is "What don't you understand about the DFT?"

    People here are tolerant and very much used to helping people who haven't done math in a long time. You're not alone! But there's something not right if whoever is helping you is working harder than you are.
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  9. #9
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    have worked it out. thank you.
    Last edited by retroscience; November 11th 2010 at 11:40 AM.
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  10. #10
    MHF Contributor Bruno J.'s Avatar
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    Where it says x_1 and x_1 it should be written x_2 and x_3 as you noticed.

    I'm not sure I understand the second question.
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  11. #11
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    oh yes and in the second part, im not 100% sure on how he got 1-i, its the "i" thats bothering me, how did he remove the exponential?
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  12. #12
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    got it! will post my complete solution online very soon!
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  13. #13
    MHF Contributor Bruno J.'s Avatar
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    Quote Originally Posted by retroscience View Post
    oh yes and in the second part, im not 100% sure on how he got 1-i, its the "i" thats bothering me, how did he remove the exponential?
    Good!
    It's because of Euler's formula : e^{i\theta}=\cos \theta + i\sin \theta.
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