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  1. #1

    ziggy/math/eng peopel

    i'm stupid

    why does the radius of convergence remain unchanged when you differentiate or integrate a power series, even though the interval of convergence/endpoints can change. proof/theorem/explanation/etc?



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  2. #2

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    Quote Originally Posted by Brood_Star View Post
    i'm stupid
    yep <3

  3. #3
    i aint even know what the formal definition of the radius is other than between the two endpoints

    i googled it and all i found was some lim sup (beta) problem and that aint very helpful

    sorry to reinforce nadota stupidity stereotypes



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  4. #4

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    pretty sure it's not a stereotypes.

  5. #5
    why yall gotta be so negative all the time



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  6. #6

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    why you talk like you're from tennessee?

  7. #7
    why u got a koala dolphin avatar



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  8. #8

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    because i'm amazing.

    why you have to be so hip all the time ?

  9. #9
    if you would kindly define hip id be more inclined to respond

    im pretty sure u can call anything a hipster these days



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  10. #10

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    too lazy to find a definition but these are lyrics from a 1947 song by Harry "The Hipster" Gibson

    Hey you know there's a lot of talk going around about this hip and hep jive. Lots of people are going around saying "hip." Lots of squares are coming out with "hep." Well the hipster is here to inform you what the jive is all about.

    The jive is hip, don't say hep
    That's a slip of the lip, let me give you a tip
    Don't you ever say hep it ain't hip, NO IT AIN'T
    It ain't hip to be loud and wrong
    Just because you're feeling strong
    You try too hard to make a hit
    And every time you do you tip your mitt
    It ain't hip to blow your top
    The only thing you say is mop, mop, mop
    Keep cool fool, like a fish in the pool
    That's the golden rule at the Hipster school
    You find yourself talking too much
    Then you know you're off the track
    That's the stuff you got to watch
    Everybody wants to get into the act
    It ain't hip to think you're "in there"
    Just because of the zooty suit you wear
    You can laugh and shout but you better watch out
    Cause you don't know what it's all about, man
    Man you ain't hip if you don't get hip to this hip and hep jive
    Now get it now, look out
    Man get hip with the hipster, YEAH! Got to do it!
    be hip not hep, coz hep is not hip
    so just be hip and pray you dont slip!


    this is great i really feel us bonding and becoming closer to each other. hope nobody crashes our intimate exchanges.

  11. #11
    aint wanna read it cause i just wanna study but i agree and more importantly hope someone answers the original question



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  12. #12
    Wicked Sick 1300's Avatar
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    S = sum over n of c_n * x^n => r = lim n->inf c_n/c_n+1

    d/dx S = sum over n of n * c_n * x^(n-1) => r = lim n->inf n*c_n/((n+1)*c_(n+1)) = lim n->inf c_n/c_n+1

    integral S dx = sum over n of c_n * ^(n+1) / (n+1) => r = lim n->inf (c_n/(n+1))/(c_(n+1)/(n+2)) = lim n->inf c_n/c_n+1

    all three r's are the same

    if you're asking for some fundamental reason then iunno ask some math major

  13. #13
    nope, that makes sense



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  14. #14
    Double Kill
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    Quote Originally Posted by Brood_Star View Post
    if you would kindly define hip id be more inclined to respond

    im pretty sure u can call anything a hipster these days
    http://d24w6bsrhbeh9d.cloudfront.net...48358_460s.jpg

  15. #15
    First, you can only differentiate and integrate term by term for certain functions... too lazy to do the proof myself so read:
    http://www.dpmms.cam.ac.uk/~agk22/uniform.pdf

    Second the complex analysis way of thinking about the radius of convergence is that the radius of convergence is the distance from xo to the nearest singularity in the complex plane. [example: the taylor series for the function f(x) = 1/(x^2+1) has radius of convergence 1 because the nearest singularities in the complex plane are +i and -i which are both one unit from the origin]

    what class is this for, complex analysis[it can't be for diffeq cus u already took that]? And why the fuck would you have to take that as an engineering major.

  16. #16
    there's a mandatory complex analysis class in 3rd year but it was just a random power series review q

    e: are you not an engineer? i just assumed u were from what 5-s told me
    Last edited by Brood_Star; April 15th, 2012 at 03:12 AM.



    Arteezy: my stupid fucking dad's classical music is distracting me how am i supposed 2 concentrate

  17. #17
    lmfao is this a real question?

    Spoiler

  18. #18
    Wicked Sick 1300's Avatar
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    Quote Originally Posted by saga16 View Post
    First, you can only differentiate and integrate term by term for certain functions... too lazy to do the proof myself so read:
    http://www.dpmms.cam.ac.uk/~agk22/uniform.pdf

    Second the complex analysis way of thinking about the radius of convergence is that the radius of convergence is the distance from xo to the nearest singularity in the complex plane. [example: the taylor series for the function f(x) = 1/(x^2+1) has radius of convergence 1 because the nearest singularities in the complex plane are +i and -i which are both one unit from the origin]

    what class is this for, complex analysis[it can't be for diffeq cus u already took that]? And why the fuck would you have to take that as an engineering major.
    ur link doesnt apply, its fucking power series lol
    though im sure you can find some cool intuition about this radius of convergence issue with complex analysis

    cant comment on it, all i remember doing is a shitton of useless contour integrals
    Last edited by 1300; April 15th, 2012 at 03:28 AM.

  19. #19
    Quote Originally Posted by Brood_Star View Post
    there's a mandatory complex analysis class in 3rd year but it was just a random power series review q

    e: are you not an engineer? i just assumed u were from what 5-s told me
    Im an engineer but getting a double major in something else[not engineering] that requires tons of stupid math/physics

    and 1300 it applies unless im being retarded. although I just realized now I really didn't answer his question.

  20. #20
    howd u not just come to me brah

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