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: Determine the point(s) of inflection in the equation

  1. Jul 28, 2006 #1
    I dont know if i'm posting in the wrong section, because I'm doing this intoductory calculus at high school level:

    Anyways heres my question:

    Determine the point(s) of inflection in the equation:

    y = e^x + e^-x

    I know that you have to find y'' and isolate for x to find point(s) of inflection.

    My work (sorry if its a pain to read, I dont know how to use latex)

    y=e^x + e^-x

    y' = [ (e^x)(x) ] + [ (e^-x)(-x) ]

    y'' = [ (e^x)(x)(1) ] + [ (e^-x)(-x)(-1) ]
    y'' = (e^x)(x) + (e^-x)(x)
    y'' = x(e^x + e^-x)

    I'm stuck here.
     
  2. jcsd
  3. Jul 28, 2006 #2

    HallsofIvy

    User Avatar
    Science Advisor

    No!! The derivative of e^x is e^x, not "(e^x)(x)". The derivative of e^(-x) is -e^(-x) not "e^(-x)(-x)".

     
  4. Jul 28, 2006 #3
    Whoops i got confused, I thought derivative of e^f(x) was [e^f(x)] x f(x)

    thanks
     
  5. Jul 28, 2006 #4

    Office_Shredder

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    it's e^f(x)*f '(x)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook