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

Prove these innequalities

  1. Feb 11, 2009 #1
    http://img131.imageshack.us/img131/1323/29081539pt7.th.gif [Broken]

    how am i supposed to prove that the function is bigger then its tailor series??

    the taylor series are written in endless way.
    its should be equal

    how to prove that its bigger??

    for the first i tried prove by induction:

    the base case
    f_1(x) = e^x - \left( 1 + x\right)\\
    i know that x>0
    but it doesnt prove that
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 11, 2009 #2


    User Avatar
    Science Advisor

    You need to recognize that the problem is NOT to proved "the function is bigger then its tailor series". Both of these functions are "analytic" and so they are equal to their Taylor series. You are asked to show that the functions are greater than the Taylor polynomial up to power n, in the first case, and to second power for the second. The right sides are finite sums.

    Since each function is equal to its Taylor series, the only difference is that the Taylor polynomial, of order n, is missing all terms past n.

    If x> 0 all those missing terms are positive. (In the middle of your post you say "I know that x>0". HOW do you know that? Is it a condition of the problem? You don't mention that!)
  4. Feb 13, 2009 #3
    you are correct i wasnt given that x>0
    so my general function are bigger then their taylor series by the remainder of Rn

    this is the logic
    how to formulate it into equation??
  5. Feb 14, 2009 #4
    how to prove it?
  6. Feb 14, 2009 #5
    how to prove it?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook