Results 1 to 3 of 3

Math Help - How do i find the inverse of Log functions???

  1. #1
    Newbie
    Joined
    May 2008
    Posts
    12

    Smile How do i find the inverse of Log functions???

    Hi!!

    Im trying to teach myself how to do the inverse of ln functions, so most of what I know is only from my book :P

    So this is the question,



    f(x) = 2ln[(x^2)/3]+ 3

    the thing is how do i get the inverse of ln? do i multiply it by 'e' if the inverse of 'e' is ln 'e'?


    Thanks@!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1
    Quote Originally Posted by appleseed View Post
    Hi!!

    Im trying to teach myself how to do the inverse of ln functions, so most of what I know is only from my book :P

    So this is the question,






    the thing is how do i get the inverse of ln? do i multiply it by 'e' if the inverse of 'e' is ln 'e'?


    Thanks@!

    The inverse of \ln(x) is e^x but only for x>0. This is because the log of a negative number is undefined.

    More generally if f(x) = \log_b(x) \: , b \neq 0,1 \: , \: x >0 \text{  then  } f^{-1}(x) = b^x
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,525
    Thanks
    1384
    Quote Originally Posted by appleseed View Post
    Hi!!

    Im trying to teach myself how to do the inverse of ln functions, so most of what I know is only from my book :P

    So this is the question,






    the thing is how do i get the inverse of ln? do i multiply it by 'e' if the inverse of 'e' is ln 'e'?


    Thanks@!
    There are two things wrong with this- you do not "multiply" by anything, you take the exponential function- that is e to that power.

    Also it makes no sense to say "the inverse of 'e' is ln 'e'". "e" is a number, not a function. The inverse of the function exp(x)= e^x is ln(x) and so the inverse function of ln(x) is e^x:

    e^{ln(x)}= x and ln(e^x)= x.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: February 13th 2010, 09:09 PM
  2. Replies: 2
    Last Post: October 19th 2009, 02:47 AM
  3. Find Inverse of Radical Functions
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: November 9th 2008, 05:24 AM
  4. Using inverse trig functions to find angles
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: November 3rd 2007, 07:27 PM
  5. Inverse Functions
    Posted in the Calculus Forum
    Replies: 5
    Last Post: March 14th 2007, 04:06 PM

Search Tags


/mathhelpforum @mathhelpforum