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-   -   Prove the Vertical asymptotic (https://www.askmehelpdesk.com/showthread.php?t=544865)

  • Jan 17, 2011, 05:55 AM
    pop000
    1 Attachment(s)
    Prove the Vertical asymptotic
    I have an Function (in the picture) and I need to Prove if X=0 can be a Vertical asymptotic
    so I tried to use in L'Hôpital's rule but is not Possible Because I not get 0/0 or -+Infinity/+-Infinity.

    so how can I prove it?

    and more little thing tell me if I correct that X=1 is can't be an Vertical asymptotic

    thanks for help :)
  • Jan 17, 2011, 07:12 AM
    jcaron2
    If you rewrite the cot function as cos/sin, you'll see that the denominator really DOES go to zero.
  • Jan 17, 2011, 07:56 AM
    pop000
    Comment on jcaron2's post
    so there is not Vertical asymptotic for x=0 what about x=1 I calculated it and I found that there is no Vertical asymptotic when x=1 is correct?
    thank you
  • Jan 17, 2011, 08:46 AM
    jcaron2
    Comment on jcaron2's post
    Yes, correct in both cases. Good job! But there ARE asymptotes at x= +/- 2, +/- 4, +/- 6,.
  • Jan 17, 2011, 10:31 AM
    pop000
    Comment on jcaron2's post
    hi. I still dosen't Success to calculated for x=0 can you Please show me any way to prove that there is no Vertical asymptotic for x=1 ?

    really thank you.
  • Jan 17, 2011, 10:41 AM
    pop000
    Comment on jcaron2's post
    oh sorry I mean if you can show me any way to prove that there is no Vertical asymptotic for x=o.

    thanks.
  • Jan 17, 2011, 10:52 AM
    ebaines

    pop000: Use l'Hospital's rule. The derivative of the numerator for x=0 is 1, and the derivative of the denominator for x = 0 is -pi/2. So the limit as x goes to 0 is -2/pi.
  • Jan 17, 2011, 11:07 AM
    Unknown008

    That image is small >.<



    A strange graph that is... (http://www.wolframalpha.com/input/?i=y+%3D+\frac{x+cot+(\frac{\pi+x}{2})}{x^3+-+1})

    Applying L'Hopital's rule (if I do that right... )



    But that graph is another strange one :eek:
  • Jan 17, 2011, 11:22 AM
    ebaines

    Here's how I applied l'hospital:

  • Jan 17, 2011, 11:28 AM
    Unknown008

    Ah, I kept the cot in the numerator and gave me -1/sin^2(pi x/2)

    It seems strange to me though of how a different result is obtained beginning with the same function but applying l'Hopital's rule a 'different' way...
  • Jan 17, 2011, 12:07 PM
    ebaines

    Applying l'Hospital to the equation in its original form doesn't work too well:



    You can apply l'Hospital again, but it gets really messy and I gave up on it.
  • Jan 17, 2011, 12:09 PM
    Unknown008

    Oops, seems I didn't do it well :o

    Thanks!
  • Jan 17, 2011, 12:22 PM
    pop000
    Comment on Unknown008's post
    Yes I also saw this graph and I am not see there any Vertical asymptotic. :)
  • Jan 17, 2011, 12:40 PM
    pop000
    Comment on ebaines's post
    Nice, thank.

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