Results 1 to 5 of 5

Math Help - How to Plot a 'sum' function

  1. #1
    Newbie
    Joined
    May 2009
    Posts
    21

    How to Plot a 'sum' function

    Hi all ,
    I'm a newbie with the Mathematica program . I'm trying to draw the function in the photo .

    N=10
    -2<t<2

    In the second image you can see what I wrote . nonetheless ,I got a message says: Syntax::sntxi: Incomplete expression; more input is needed.

    What am I doing wrong ?

    Thanks (:
    Attached Thumbnails Attached Thumbnails How to Plot a 'sum' function-12.gif   How to Plot a 'sum' function-13.gif  
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Aug 2008
    Posts
    903
    Quote Originally Posted by new guy View Post
    Hi all ,
    I'm a newbie with the Mathematica program . I'm trying to draw the function in the photo .

    N=10
    -2<t<2

    In the second image you can see what I wrote . nonetheless ,I got a message says: Syntax::sntxi: Incomplete expression; more input is needed.

    What am I doing wrong ?

    Thanks (:
    Don't use brackets for the exponential. Just use parenthesis. Also, should specify explicitly the Re or Im component of the function like:

    Code:
    Plot[Re[Sum[E^(2*Pi*I*k*t), 
        {k, -10, 10}]], {t, -2, 2}]
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by shawsend View Post
    Don't use brackets for the exponential. Just use parenthesis. Also, should specify explicitly the Re or Im component of the function like:

    Code:
    Plot[Re[Sum[E^(2*Pi*I*k*t), 
        {k, -10, 10}]], {t, -2, 2}]
    It is already real, it just needs simplifying.

    CB
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    May 2009
    Posts
    21
    First of all thank you both .

    Second ,how do know that it needs to be Re and not Im ?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by new guy View Post
    First of all thank you both .

    Second ,how do know that it needs to be Re and not Im ?
    because if you pair terms with positve and negative indices of the same magnitude one is the conjugate of the other, and so such pairs have a real sum.

    CB
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. matlab plot function
    Posted in the Math Software Forum
    Replies: 4
    Last Post: May 26th 2010, 08:03 AM
  2. Plot a function
    Posted in the Math Software Forum
    Replies: 2
    Last Post: May 23rd 2009, 01:06 AM
  3. How can I make a plot of this function?
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 16th 2009, 08:55 AM
  4. plot complex function
    Posted in the Calculus Forum
    Replies: 2
    Last Post: January 28th 2008, 11:35 AM
  5. plot of a function of time
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 26th 2007, 10:10 AM

Search Tags


/mathhelpforum @mathhelpforum