Limit using l'hopitals rule

  • Thread starter magnifik
  • Start date
  • #1
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Homework Statement


Find the limit as x goes to 1 of tan(pi*x/2)lnx


Homework Equations


using l'hopitals, lim f'(x)/g'(x)=answer


The Attempt at a Solution


i tried integrating by making the tangent part squared so i can divide by the tangent part, but i keep getting stuck. i think the answer is either 1 or infinity.

help please? thanks
 

Answers and Replies

  • #2
Dick
Science Advisor
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I really don't know how you are trying to do the problem. l'Hopital's rule doesn't tell you to integrate anything. Write it as ln(x)/cot(pi*x/2). Now it's a 0/0 form. Now differentiate numerator and denominator like l'Hopital says.
 
  • #3
360
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woops i meant taking the derivative
 
  • #4
35,008
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Integrating has nothing to do with this problem. Try rewriting your limit as
[tex]\lim_{x \to 1}\frac{ln(x)}{cot(x*\pi/2)}[/tex]

Now you have something you can use L'Hopital's Rule on.
 

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