1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Could you check this please

  1. Sep 27, 2005 #1

    equation for the axis of symmetry???
    I got x=pi

    f(x)=ln(x^2 - 20)

    describe symmetry??

    I got symmetric arround y axis.


    I got y=sqr of ((x/ln) +20)



    I got y= sqr of (x/ln)
  2. jcsd
  3. Sep 27, 2005 #2


    User Avatar
    Homework Helper

    Since cos x is a repeating function, it has an infinite number of axes of symmetry. They occur at n pi. Something similar needs to be done for exp(cos x).

    For the others, you seem to be using "ln" as a variable of some sort. Remember that ln x is a function, with inverse exp(x). You might want to look at those again.
  4. Sep 27, 2005 #3
    So for others I just change ln to exp?
  5. Sep 27, 2005 #4
    So I get f(x)^-1=e^(X^2-20)


  6. Sep 28, 2005 #5


    User Avatar
    Homework Helper

    Let me take one of them. You should be able to do the rest.

    y = ln(x^2 - 20)

    exp(y) = x^2 - 20

    x^2 = exp(y) + 20

    x = sqrt(exp(y) + 20)

    So, f^-1(x) = sqrt(exp(x) + 20)

    Note that there are restrictions on the domain and range - these would correspond to the restrictions on the range and domain of the original function.

    Does that help?
  7. Sep 28, 2005 #6
    It does.

    Thank you so much. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook