Results 1 to 6 of 6

Math Help - finding the inverse function of ln

  1. #1
    Banned
    Joined
    Sep 2009
    Posts
    8

    finding the inverse function of ln

    Find a formula for the inverse of the function.
    y = ln(x + 1)

    I know that the inverse of ln(x) = e^x, but i cant figure out how to solve the inverse of ln(x+1). I tried checking my work by plugging in 3 for x and seeing if my inverse function puts out the result of ln(3+1) but no luck. Any ideas?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Apr 2008
    Posts
    191
    Quote Originally Posted by evankimia View Post
    Find a formula for the inverse of the function.
    y = ln(x + 1)

    I know that the inverse of ln(x) = e^x, but i cant figure out how to solve the inverse of ln(x+1). I tried checking my work by plugging in 3 for x and seeing if my inverse function puts out the result of ln(3+1) but no luck. Any ideas?
    What about f^{-1}(x)= e^x-1?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Banned
    Joined
    Sep 2009
    Posts
    8
    yes that did work. I just forgot alot of algebra. The method for getting e^x-1 would just be subtracting 1 by both sides then just putting in the inverse of ln(x) (which is e^x)?

    also, how would i go about finding (f - 1)(1) and f(f -1)(1) of this? i know arctan is the inverse of tan..
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Apr 2008
    Posts
    191
    Quote Originally Posted by evankimia View Post
    yes that did work. I just forgot alot of algebra. The method for getting e^x-1 would just be subtracting 1 by both sides then just putting in the inverse of ln(x) (which is e^x)?
    That's correct.

    also, how would i go about finding (f - 1)(1) and f(f -1)(1) of this? i know arctan is the inverse of tan..
    I don't quite understand the question. If you want to find the inverse of

    f(x) = 1 + x^2 + tan(\frac{\pi x}{2}) then you must write it as:

    y = 1 + x^2 + tan(\frac{\pi x}{2}) and then change the subject of the formula (i.e. solve for x), so that it reads x=...
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Banned
    Joined
    Sep 2009
    Posts
    8
    how would i go about extracting the x from the tan(pie x/2)?

    I found out that f-1(1) is 0, but am not sure how. if anyone has an explanation it would be great appriciated.
    Last edited by mr fantastic; September 27th 2009 at 03:24 AM. Reason: Merged posts
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by evankimia View Post
    how would i go about extracting the x from the tan(pie x/2)?

    I found out that f-1(1) is 0, but am not sure how. if anyone has an explanation it would be great appriciated.
    The inverse cannot be found in terms of elementary functions. Read here: http://www.mathhelpforum.com/math-he...-function.html
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding the inverse of a function
    Posted in the Algebra Forum
    Replies: 12
    Last Post: June 24th 2011, 04:46 AM
  2. Finding inverse function
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: December 7th 2009, 05:50 PM
  3. Finding the inverse of a function
    Posted in the Algebra Forum
    Replies: 1
    Last Post: September 11th 2009, 05:28 PM
  4. Finding the inverse function
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: February 8th 2009, 03:35 PM
  5. Finding the inverse of a function
    Posted in the Algebra Forum
    Replies: 1
    Last Post: December 29th 2007, 06:14 PM

Search Tags


/mathhelpforum @mathhelpforum