Results 1 to 4 of 4

Math Help - basic logarithm question

  1. #1
    Newbie
    Joined
    Dec 2009
    Posts
    6

    basic logarithm question



    How do you get that lower equation from the upper one?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    Hi

    Take the natural log of the upper equation

    \ln \left(e^{-kt}\right) = \ln \frac12

    ln being the inverse function of exp, \ln(e^x) = x

    The equation becomes

    -kt = \ln \frac12
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Dec 2009
    Posts
    6
    thanks.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Also \ln \left(\frac{1}{2}\right) = \ln (2^{-1}) = -\ln(2)

    So kt = \ln(2) which is a more usual form in exponential decay
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. logarithm question
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: December 5th 2011, 10:42 AM
  2. Logarithm question
    Posted in the Algebra Forum
    Replies: 6
    Last Post: April 6th 2010, 02:43 PM
  3. Basic Logarithm Problem
    Posted in the Algebra Forum
    Replies: 3
    Last Post: November 27th 2009, 01:30 PM
  4. basic logarithm problem
    Posted in the Algebra Forum
    Replies: 1
    Last Post: March 16th 2008, 07:02 PM
  5. [SOLVED] Logarithm Question
    Posted in the Math Topics Forum
    Replies: 2
    Last Post: January 18th 2006, 09:39 AM

Search Tags


/mathhelpforum @mathhelpforum