Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Ln limit result question

  1. Feb 12, 2009 #1
    [tex]
    \lim_{x->3^-} ln^2(9-x^2)=+\infty
    [/tex]
    the meaning of this ln is e^+infinity=closser to 0

    how is that??

    by my math e^+infinity is infinity
     
  2. jcsd
  3. Feb 12, 2009 #2
    As x approaches three, then ln(9 - x^2) approaches 0 and so the value goes to negative infinity, squaring it gives you positive infinity.
     
  4. Feb 12, 2009 #3

    Mark44

    Staff: Mentor

    Not quite. As x approaches 3 from below, 9 - x^2 approaches 0, from the positive side, so ln(9 -x^2) approaches negative infinity, so [ln(9 - x^2)]^2 approaches positive infinity.
     
  5. Feb 12, 2009 #4
    Oops, I meant to say that the value within the ln approaches 0 and so ln approaches negative infinity, which when squared is positive infinity.
     
  6. Feb 12, 2009 #5

    Mark44

    Staff: Mentor

    Happens to the best of us :smile:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook