Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

sat_chen

find this limit using the l hopital rule

  • one year ago
  • one year ago

  • This Question is Closed
  1. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1361572558530:dw|

    • one year ago
  2. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    i know if you just plug in the value you get 0/0 so you use the rule

    • one year ago
  3. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    so i use the rule and get |dw:1361572627877:dw|

    • one year ago
  4. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    how do i get from here as you cant use the trigonometric substitution either

    • one year ago
  5. walters
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1361572546361:dw|

    • one year ago
  6. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    the derivative of tan is sec^2 x lol

    • one year ago
  7. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    so thats wrong

    • one year ago
  8. walters
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1361572818037:dw| then differentiate from here

    • one year ago
  9. experimentX
    Best Response
    You've already chosen the best response.
    Medals 1

    the limit goes to -infinity

    • one year ago
  10. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    Change your 1 -sec^2x into -tan^2x and see if that helps you simplify your ratio.

    • one year ago
  11. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    thats not how it works youcan never change 1 - sec^2 into tan^2x

    • one year ago
  12. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    you can change it into -tan^2x though, not tan^2x

    • one year ago
  13. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    ok im gonna try walters method

    • one year ago
  14. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    But that only makes it worse. Nevermind. Hang on.

    • one year ago
  15. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    you dont understand tan^2 x + 1 = sec^2x try to change it to what you just did it never works

    • one year ago
  16. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    Move the 1 over, and then multiply both sides by a -1.

    • one year ago
  17. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    i thought about your method walter but its x not 1 - tanx

    • one year ago
  18. experimentX
    Best Response
    You've already chosen the best response.
    Medals 1

    Without using L'hopital |dw:1361573289043:dw|

    • one year ago
  19. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    so the solution is 1/0 but thats not gonna work either

    • one year ago
  20. experimentX
    Best Response
    You've already chosen the best response.
    Medals 1

    or I could have misunderstood your question http://www.wolframalpha.com/input/?i=lim+x-%3E0+sin%28x%29%2F%28x-tan%28x%29%29

    • one year ago
  21. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    If you use L'hopital's rule twice, you end up with the limit as x approaches negative infinity of cos^3x/(-2)

    • one year ago
  22. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    no that is the question experimentX

    • one year ago
  23. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    oops, it's approaching zero, so the answer is -1/2

    • one year ago
  24. walters
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1361573583223:dw|

    • one year ago
  25. experimentX
    Best Response
    You've already chosen the best response.
    Medals 1

    You can't use L'hopital rule twice, one you use L'hopital rule, ... the top is cos(x) ... which is 1 and the bottom part is still 0.

    • one year ago
  26. experimentX
    Best Response
    You've already chosen the best response.
    Medals 1

    *once

    • one year ago
  27. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    Ah hell, then it's no longer of indeterminate form.

    • one year ago
  28. walters
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1361573754561:dw|

    • one year ago
  29. experimentX
    Best Response
    You've already chosen the best response.
    Medals 1

    the best way see through limits is to expand using Taylor series. Try expanding it ... the answer is pretty obvious. Anyway gotta sleep ... best of luck.

    • one year ago
  30. sat_chen
    Best Response
    You've already chosen the best response.
    Medals 0

    i think i got it now ty a lot

    • one year ago
  31. calmat01
    Best Response
    You've already chosen the best response.
    Medals 0

    I need to go refresh my memory. Good luck to you.

    • one year ago
    • Attachments:

See more questions >>>

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.