Results 1 to 3 of 3

Math Help - laplace transform(t^2cos(t))=

  1. #1
    Member
    Joined
    Sep 2010
    Posts
    149
    Thanks
    3

    laplace transform(t^2cos(t))=

    = (-1)^2 (d^2/ds^2) laplace(cos(t))

    = (d^2/ds^2) (s/(s^2+1))

    = (d/ds) [-2s^2(s^2+1)^-2 + (s^2+1)^-1]

    = 8s^3/ (s^2+1)^3 - 6s/(s^2+1)^2

    thats the answer i got but the answer in the book says (2s^3 - 6s)/ (s^2+1)^3

    where did i go wrong?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Rhymes with Orange Chris L T521's Avatar
    Joined
    May 2008
    From
    Santa Cruz, CA
    Posts
    2,844
    Thanks
    3
    Quote Originally Posted by linalg123 View Post
    = (-1)^2 (d^2/ds^2) laplace(cos(t))

    = (d^2/ds^2) (s/(s^2+1))

    = (d/ds) [-2s^2(s^2+1)^-2 + (s^2+1)^-1]

    = 8s^3/ (s^2+1)^3 - 6s/(s^2+1)^2

    thats the answer i got but the answer in the book says (2s^3 - 6s)/ (s^2+1)^3

    where did i go wrong?
    You didn't go wrong anywhere!! Just combine the two fractions you got to get the desired result!!
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Sep 2010
    Posts
    149
    Thanks
    3
    ughh..duhhh.. thanks
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Laplace transform of |sin(t)| ?
    Posted in the Calculus Forum
    Replies: 23
    Last Post: January 3rd 2011, 03:14 PM
  2. Laplace transform and Fourier transform what is the different?
    Posted in the Advanced Applied Math Forum
    Replies: 8
    Last Post: December 29th 2010, 10:51 PM
  3. Laplace Transform
    Posted in the Differential Equations Forum
    Replies: 3
    Last Post: November 22nd 2010, 05:29 AM
  4. Laplace transform
    Posted in the Differential Equations Forum
    Replies: 4
    Last Post: September 4th 2009, 03:21 AM
  5. Laplace Transform
    Posted in the Differential Equations Forum
    Replies: 1
    Last Post: April 14th 2009, 06:35 PM

Search Tags


/mathhelpforum @mathhelpforum