L'hopital's rule Definition and 115 Threads

  1. P

    Use L'Hopital's rule to evaluate the limit

    Homework Statement Use L'Hopital's rule to evaluate the limit: lim (x/(x+1))^x x>infinite Homework Equations The Attempt at a Solution I put it into a logarithm first to make it the limit of xln(x/(x+1)) then I took the derivative and got [(1/x)-(1/(x+1))]/[x^-2] but its still...
  2. R

    Solving Limit Problems with L'Hopital's Rule

    Homework Statement (a) Explain why L'Hopital's rule does not apply to the problem lim_{x\rightarrow0} [ (x^{2}sin(1/x)) / sinx ] (b) Find the limit. Homework Equations lim _{x\rightarrow0} xsin(1/x) = 0 , by the Squeezing Theorem. lim _{x\rightarrow0} sin (1/x) Does Not Exist...
  3. N

    How Do You Find the Limit When L'Hopital's Rule Fails?

    I'm suppose to find the limit as x goes to infinity of [(9x + 1) ^ (1/2)] / [(x+1) ^ (1/2)]. L'Hopital's Rule does not work on here (it said so even in the directions) as the function keeps on cycling. ...they gave us the answer (3) but I need to find out how. :S
  4. C

    L'Hopital's Rule: Solving Limits of x Approaching 0

    I would like to know if I did these the correct way. Homework Statement 1.lim x->0 (1/sin 2x)-1/2x. the answer is 0. 2.lim x->0 (x^-5*ln x). The answer is -infinity. Homework Equations 1.I used L'Hopitals theorem 2.I derived them, than L'hopitals. The Attempt at a Solution 1.I...
  5. S

    Solving an Infinite Limit with L'Hôpital's Rule

    Im trying to solve this problem using l'hopital but amm not sure how to do it lim X->infinite x^3 * e^(-x^2) soo this infinite * e^-infinite... but from there I am not sure if you can use it to solve this...
  6. A

    L'Hopital's Rule - I'm loosing my hair

    L'Hopital's Rule - I'm loosing my hair! Ok, I have the following: Lim x->0 sqrt(4-x^2) -2 /x After I change the equation to remove the radicle, I get: Lim x->0 ((4-x^2)^1/2 - 2)/x but when I apply the rule the, I'm loosing it I thought I should get: 1/2 ((4-x^2)^-1/2 times...
  7. M

    L'Hopital's Rule for Solving Limits

    Homework Statement lim as x->0 (tan(x)-x)/(sin2x-2x) Homework Equations L'Hopitals rule states that if the limit reaches 0/0, you can take the derivative of the top and the bottom until you get the real limit. The Attempt at a Solution (sec^2(x)-1)/(2cos2x-2) still 0/0...
  8. N

    Evaluate Limit with L'Hôpital's Rule: x => 0 of sqrt(x^2+x) - x

    evaluate the limit as x=>0 of sqrt(x^2+x) - x so i multiplied by the conjugate to get: x^2 + x - x^2 / sqrt(x^2 +x) + x which simplifies to: x / sqrt (x^2 + x) + x = infinity/infinity taking LH, you get: 1 / 1/2(x^2+x)^(-1/2) * (2x+1) + 1 = infinity/infinity again looking...
  9. V

    L'Hopital's Rule, 2 Confusing ones

    Hey, So I'm having a bit of difficulty with two of these L'Hospital's Rule problems... The first: \mathop {\lim }\limits_{x \to \infty} (\sqrt{x^2 + x} - x) So when you have an indefinite form \infty - \infty, you've got to turn it into a product indefinite form, usually something like \infty...
  10. S

    Use L'Hopital's Rule to evaluate the limit

    Hi. Use L'Hopital's Rule to evaluate the limit. lim x-infinity of (lnx) ^(2/x) The answer is 1. I kept taking the derivative but it seemed like I was going around in circles. Any help would be appreciated. Thanks
  11. M

    L'Hopital's rule for solving limit

    1. lim [(1+x)^(1/x) - e ] / x x ->0 2. lim [sin(2/x)+cos(1/x)]^x x -> inf help...
  12. Z

    When Can i apply L'Hopital's rule?

    I am trying to work through the following problem: if function is differentiable on an interval containing 0 except possibly at 0, and it is continuous at 0, and 0= f(0)= lim f ' (x) (as x approaches 0). Prove f'(0) exists and = 0. I thought of using the definition of a limit to get to lim [...
  13. C

    What is the logic behind L'Hopital's Rule?

    Can anyone tell me, what is the rationale behind L'Hopital's Rule? I just know that how to use it but don't know why it is logic.
  14. M

    L'Hopital's rule graph problem

    Why can't I solve this? \lim_{x\rightarrow 0} \frac{\sqrt{1+\tan(x)}-\sqrt{1+\sin(x)}}{x^3}
  15. K

    Solving a Question on L'Hopital's Rule

    Having trouble with a question on L'Hopital's rule. I have never come across it must have misseda lecture. From what I understand the rule approximates values at a limit. Here's what I have anyway. I've derived a velocity gradient for a spherically symmetric, isothermal stellar wind as...
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