Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The Hospital Confusion :smile:

  1. Jan 6, 2007 #1
    Hey, I have this problem where i am trying to find the limit of the equation:


    when n--->0

    I used the l-hospital rule to solve it and got

    ---------------- = 1

    The answer is supposed to be 0 and using another method it proved so!!
    So what am i doing wrong :cry:
  2. jcsd
  3. Jan 6, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    I'd like to see that proof, since it is well-known that (when x is in radians):
    [tex]\lim_{x\rightarrow 0}\frac{\sin (x)}{x} = 1[/tex]

    (I don't think you are wrong.)
  4. Jan 6, 2007 #3

    Gib Z

    User Avatar
    Homework Helper

    Yea me too, Looks correct.
  5. Jan 7, 2007 #4
    [tex] \lim_{x\rightarrow 0}\frac{2\sin (\frac{1}{2} n\pi)}{n\pi} =

    2*\frac{1}{2}\lim_{x\rightarrow 0}\frac{\sin (\frac{1}{2} n\pi)}{\frac{1}{2} n\pi} = 1 [/tex]

    hope the latex works
  6. Jan 7, 2007 #5


    User Avatar
    Staff Emeritus
    Science Advisor

    In other words, WHO told you "The answer is supposed to be 0"? The limit is clearly 1.
  7. Jan 7, 2007 #6
    can someone tell me how to post the question form a world document as i formulated the question there!! or how can i paste formulas here?

    Attached Files:

    Last edited: Jan 7, 2007
  8. Jan 12, 2007 #7
    YOu can see that also from the Taylor series: sin(x) = x-x^3/6+x^5/120-+-
  9. Jan 12, 2007 #8


    User Avatar
    Science Advisor
    Homework Helper

    I don't see what prescript you used to get to C_{n} in the first place. And why you think it should work to give you C_{0} in the same manner.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: The Hospital Confusion :smile:
  1. Cancelling confusion (Replies: 2)

  2. Gaussian confusion! (Replies: 3)

  3. Boundness confusion (Replies: 9)

  4. Exponent confusion. (Replies: 2)