Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Inquiring About Something

  1. Feb 29, 2008 #1
    Does anyone here know what the indefinite integal of 1/e^x is?

    Im an new member and, this is my first post.
  2. jcsd
  3. Feb 29, 2008 #2
    i guess u have posted on the wrong forum, but anyways!

    [tex]\int e^{-x} dx= -e^{-x}+c[/tex]
  4. Feb 29, 2008 #3
    here it is how you might want to think about it: i am assuming you know how to integrate this, since it is only a tabelar integral
    [tex]\int e^{x}dx[/tex], for the other one[tex]\int e^{-x}dx[/tex], take the substitution -x=t, so now we have dx=-dt, now substitute back on the integral we get:
    [tex]\int e^{t}(-dt)=-\int e^{t}dt=-e^t+c [/tex] substituting back for the original variable we get [tex] -e^{-x}+c[/tex]
  5. Feb 29, 2008 #4


    User Avatar
    Homework Helper
    Gold Member

    Why not just let u = e^-x?

    No need for substitution here.
  6. Feb 29, 2008 #5
    yeah, i know, but since the op was not able to integrate e^-x, i was assuming that approaching this problem like i did, it would make it easier for him/her to understand!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook