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

Property Function exp

  1. Aug 25, 2010 #1
    How can prove this


    using [tex]\displaystyle\sum_{i=0}^n{(1/k!)A^kt^k}[/tex]

    and this properties
    in t=0
    [\exp(At)]_{t} = I

    Last edited: Aug 26, 2010
  2. jcsd
  3. Aug 25, 2010 #2
    For your first equation, please refer to this question in http://www.voofie.com/concept/Mathematics/" [Broken]:

    http://www.voofie.com/content/152/how-to-prove-eat-e-at_0-eat-t_0/" [Broken]

    I think you typed wrong in this formula:

    [tex]exp(At)_t=0 = I[/tex]

    0 is not equal to I. And your what's your meaning of [tex]exp(At)_t[/tex]?

    For this one [tex]exp(At)exp(-At)=I[/tex], you can use my result to prove easily. For the last one, you should try to use the power series expansion and differentiate term by term. You will get the answer easily too.
    Last edited by a moderator: May 4, 2017
  4. Aug 26, 2010 #3
    To conclude, i suppose you mean

    [tex][\exp(At)]_{t=0} = I[/tex]

    Well, it's pretty simple:

    [tex][\exp(At)]_{t=0} = \left[\sum_{k=0}^\infty\frac{A^kt^k}{k!}\right]_{t=0}=I+0+0+\cdots=I[/tex]
  5. Aug 26, 2010 #4
    fix question my question is
    How prove this,
    using as above properties
  6. Aug 26, 2010 #5
    Thank,I am reading this web
    http://www.voofie.com/content/152/how-to-prove-eat-e-at_0-eat-t_0/ [Broken]

    but i dont understand how change sumatoria infinite to finite, Where i can read this?
    Last edited by a moderator: May 4, 2017
  7. Aug 26, 2010 #6
    I have answered your question. Please have a look.

    http://www.voofie.com/content/152/how-to-prove-eat-e-at_0-eat-t_0/" [Broken]
    Last edited by a moderator: May 4, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook