A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • 5 years ago

what is this limit \[\lim_{x \rightarrow \pi/2}(xcosx)\]

  • This Question is Closed
  1. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\lim_{x \rightarrow \pi/2}(xcosx)\]

  2. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    0

  3. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    mertsj do you mind demonstrating that please?

  4. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    pi/2times cospi/2=pi/2times 0 = 0

  5. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok thanks would you mind helping me with this one also

  6. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\lim_{x \rightarrow -7}(x^2 + 10x + 21/x + 7)\] i've got -98/0. i dont know what to do from there

  7. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    You can't divide by 0 so divide numerator so another approach is needed.

  8. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Factor and reduce first

  9. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok i was thinking along the lines as approach -7 from left and right

  10. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (x+7)(x+3)/(x+7)...so the x + 7 cancels and im left with x + 3

  11. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    yes

  12. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Now replace the x with -7

  13. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i see.

  14. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i have this one that is somewhat similar but you end up with 0/0 \[\lim_{x \rightarrow 1}(x^2 - 4x + 3/ x^2 + 2x -3)\]

  15. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    same approach again right? factor and reduce?

  16. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    yes

  17. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (x-3)(x-1)/ (x-3)(x+1)...?

  18. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    is that the right structure

  19. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    |dw:1326943979278:dw|

  20. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh wow im getting this thanks for the help. would you be willing to continue working with me? i have about 8 more

  21. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    I am willing but I might be a little distracted as my daughter is here and we are visiting.

  22. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok no problem

  23. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\lim_{x \rightarrow -10}(x^2 - 17x + 70/ x + 10)\]

  24. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    when i attempt this...

  25. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i get 140/0...so i take the factor and reduce approach

  26. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    and..

  27. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Yes factor and reduce

  28. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    |dw:1326944396601:dw|

  29. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (x+10)(x+7)/ (x+10)....x+7...-10+7= -3?

  30. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i keep getting my signs wrong when i factor

  31. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    It won't reduce. Did you copy it right?

  32. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    why couldnt it have been (x+10)(x+7)...it will also give you 70 right

  33. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Middle term is negative

  34. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah thats right i remember now

  35. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Did you copy it right?

  36. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    what do you mean

  37. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    it does not exist

  38. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i see that

  39. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Perhaps you wrote the problem down incorrectly

  40. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah now i understand

  41. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i have this next one...

  42. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Did you get that last one?

  43. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah

  44. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    What did you get?

  45. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\lim_{x \rightarrow 2}(x^2 - 4/2x^2 -5x + 2)\]

  46. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I got DNE (does not exist) my software accepted the answer

  47. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    how exactly would you factor the denominator in the previous problem. it is set up strangely for me

  48. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    That one should factor and reduce.

  49. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    (2x-1)(x-2)

  50. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok i was confused because i thought somehow it must add up to -5

  51. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    So you end up with (x+2)/(2x-1)

  52. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    gotcha

  53. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    next is...

  54. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\lim_{x \rightarrow 4}(\sqrt{b+0}-2/b-4)\]

  55. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    0/0

  56. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    do you still factor here? doesnt look like it

  57. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    It won't factor but why does it have sqrt(b+0) since that is just sqrt(b)?

  58. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    its sqrt (b +0)...i would guess you do 4 +0 then squared root your answer then subtract 2

  59. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    But the denominator will be 0 and that is undefined.

  60. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah i got 0/0 i was thinking theres something we could do next

  61. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    multiply the numerator and denominator by (sqrt(b)+2)

  62. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    if the numerator and denominator are both zeros. wouldnt mulitplying bring us back to square 1 with 0/0

  63. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    |dw:1326945956921:dw|

  64. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i see

  65. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1326946154087:dw|

  66. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    the limit is as x approaches -9

  67. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Multiply numerator and denominator by 9x

  68. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    |dw:1326946478456:dw|

  69. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    lim as x approaches -9 is -1/81

  70. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    thanks im almost through

  71. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Let 11x−36≤f(x)≤x2+5x−27 . Use the Squeeze Theorem to determine limx→3f(x) =

  72. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    ok but I still want to revisit that DNE one

  73. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok when we finish we can go back

  74. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    this one that i posted is a new concept so its unlike what we have been practicing so im clueless

  75. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    I see that. I have never heard of the squeeze theorem but I would assume that we should evaluate both expressions when x is 3

  76. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i got 33 and -3 respectively. what do i do with these two numbers to come up with a final answer

  77. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    You should get -3 for both of them and that is the limit. I just read it on the internet.

  78. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    redo the one you got the 33 for

  79. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah you're right i entered it incorrectly in my calculator

  80. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1326947257959:dw| as x approaches 0

  81. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    I'm not sure about this one. Unless you use a reduction formula of some sort.

  82. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok

  83. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Have you tried typing it into wolframalpha?

  84. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    L'hospital does this one easily

  85. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1326947625929:dw|

  86. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Well let's see it.

  87. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    as x approaches 0

  88. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    I'll turn you over to Turing now.

  89. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    thanks for all the help Mertsj I really appreciate it

  90. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    yw

  91. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Ask turing about that other one also

  92. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok I hope to see you around again. Enjoy

  93. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @mertsj, yes, well, done @Jinnie: do you know L'hospital's rule? derivative of top and bottom gives \[\frac{9\cos(9x)}{1}\]

  94. Mertsj
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 3

    Thanks

  95. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    hey turningtest thats my first time hearing about that rule

  96. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    can you take the derivative of sin(9x) ?

  97. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no i dont know how

  98. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Then you can't use L'hospital, which unfortunately means I can't help you as well as I hoped. I can tell you that \[\lim_{x \rightarrow 0}\frac{\sin x}{x}=1\]but proof of that are bit complicated without L'hospital's rule. All I can suggest is to try to use that fact to help you. anyway the answer is that the limit in your question is 9

  99. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok, would you be willing to do several more of these and I ask my professor about this rule next class?

  100. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    have you learned derivatives yet at all?

  101. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    nah we just started school last week

  102. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1326948473758:dw| lim as x approaches 0. this is all i need help with

  103. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    then all I can do is give answers without explanation, because the way I solve these is with a method you don't know. If you just want the answer I refer you to wolfram alpha as mertsj did. Here is your question posted there: http://www.wolframalpha.com/input/?i=limit+x+to+0+sin%289x%29%2Fx learn to use this site, but it will not help you understand, so don't rely on it.

  104. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    this last one is 1/3 try typing it into wolfram to see if I'm right

  105. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    alright thanks for the help

  106. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    im done thanks to all

  107. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    good night hope to see everyone again

  108. TuringTest
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    goodnight :)

  109. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

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.