Hey there Sign in to join this conversationNew here? Join for free

Solve this limits question for me please.

Announcements Posted on
Study Help needs new mods! 14-04-2014
Post on TSR and win a prize! Find out more... 10-04-2014
    • Thread Starter
    • 3 followers
    Offline

    ReputationRep:
    I cant do it. Tell me the method, a link to a helpful website shall be useful.

    • 3 followers
    Offline

    ReputationRep:
    (Original post by zedeneye1)
    I cant do it. Tell me the method, a link to a helpful website shall be useful.

    With identities arrange the limit to  \frac{0}{0} or \frac{\infty}{\infty} form and use the L'Hospital rule.

    1, lim_{x\rightarrow 1^+} \frac {lnx}{cos \frac{\pi x}{2}} \cdot lim_{x\rightarrow 1^+} sin \frac {\pi x}{2}

    2. Use the L"Hospital to the first limit
    the lim_{x\rightarrow 1^+} sin \frac {\pi x}{2} will canceled out
    • Thread Starter
    • 3 followers
    Offline

    ReputationRep:
    (Original post by ztibor)
    With identities arrange the limit to  \frac{0}{0} or \frac{\infty}{\infty} form and use the L'Hospital rule.

    1, lim_{x\rightarrow 1^+} \frac {lnx}{cos \frac{\pi x}{2}} \cdot lim_{x\rightarrow 1^+} sin \frac {\pi x}{2}

    2. Use the L"Hospital to the first limit
    the lim_{x\rightarrow 1^+} sin \frac {\pi x}{2} will canceled out
    oh yeah, forgot i cud use L'hospital rule.....thanks.

    but wait, doing it ur way wud give answer=1 which is not the answer...
    so wat now?
    • 1 follower
    Offline

    ReputationRep:
    (Original post by zedeneye1)
    oh yeah, forgot i cud use L'hospital rule.....thanks.

    but wait, doing it ur way wud give answer=1 which is not the answer...
    so wat now?
    you haven't used the chain rule correctly.
    • 3 followers
    Offline

    ReputationRep:
    (Original post by zedeneye1)
    oh yeah, forgot i cud use L'hospital rule.....thanks.

    but wait, doing it ur way wud give answer=1 which is not the answer...
    so wat now?
    \displaystyle \left (cos \frac{\pi x}{2}\right )' =-sin\frac{\pi x}{2} \cdot \frac {\pi}{2}
    • Thread Starter
    • 3 followers
    Offline

    ReputationRep:
    (Original post by ztibor)

    \displaystyle \left (cos \frac{\pi x}{2}\right )' =-sin\frac{\pi x}{2} \cdot \frac {\pi}{2}
    thanks i got it now...

    thank you very much, both of you guys...

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?

    this is what you'll be called on TSR

  2. this can't be left blank
    this email is already registered. Forgotten your password?

    never shared and never spammed

  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By completing the slider below you agree to The Student Room's terms & conditions and site rules

  2. Slide the button to the right to create your account

    Slide to join now Processing…

    You don't slide that way? No problem.

Updated: April 16, 2012
Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.