Results 1 to 11 of 11

Math Help - Finding area under a function using alegbraic integration

  1. #1
    Newbie
    Joined
    Aug 2008
    From
    Brisbane, Australia
    Posts
    15

    Finding area under a function using alegbraic integration

    Hi,


    I have to integrate a function and find the area underneath it. I think I've followed the procedure correctly but the numbers that I got are really strange, if anyone can help me I wud greatly appreciated it.



    P.S. If anyone has time to look at an earlier qustion that I posted that would also be greatly appreciated.[/FONT]

    http://www.mathhelpforum.com/math-he...ven-point.html
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member Showcase_22's Avatar
    Joined
    Sep 2006
    From
    The raggedy edge.
    Posts
    782
    I'm not really sure if you integrated that.

    I did this (I wrote it on the back of my notepad):



    Is that the right question?

    Also what you've written doesn't make 0.4

    0.1x(10^2)x4x10+1=401

    0.1x0x4+1=1

    401-1=400?

    What's the part that you've written under the question as well?

    You also missed the "dx" after the integral.

    I assumed you were just integrating with respect to x.
    Last edited by Showcase_22; September 4th 2008 at 02:42 AM. Reason: made a mistake.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Aug 2008
    From
    Brisbane, Australia
    Posts
    15
    That seems to make sense, it certainly is more in line with what I've found using a calculator to find the answer.

    As for whats under the question, I'm not so sure I know what you mean there.

    Perhaps it would also help if I listed the original question

    Calculate the function ( 0/10x^2+4x+1) by algebraic means; ie calculate the exact integral of your chosen function over your chosen domain.

    The domain which I am using is 0 to 10 along the x axis.

    P.S. I accidentally used multiplication symbols instead of addition symbols in my original question.

    Thanx for all the help BTW
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member Showcase_22's Avatar
    Joined
    Sep 2006
    From
    The raggedy edge.
    Posts
    782
    I meant the bit with the ln (log with a base e). I couldn't really see to which part that applied since I thought there wasn't a l/x present.

    Are you sure you mean 0? That would just make the integral of 0 that would just be 0.

    Could the question be:



    ?

    That integral is rather hard to do though
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Aug 2008
    From
    Brisbane, Australia
    Posts
    15
    Hmmm I get what you mean about the 0. I can change that to a 1 seeing how as I can choose my own function (within certain limitations). As for the log, its basically just what the rather vague explanation in my textbook said.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Super Member Showcase_22's Avatar
    Joined
    Sep 2006
    From
    The raggedy edge.
    Posts
    782
    So you chose the function:



    ?

    It is pretty hard since the quadratic can't be factorised (complex solutions) so partial fractions cannot be used. The differential of the denominator isn't on the top so natural logs are also out.

    If you can choose your own function, why don't you choose something easy???? =O
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Aug 2008
    From
    Brisbane, Australia
    Posts
    15
    Indeed I would If I could, but I have to complete it by tomorrow morning and I have used the function to differentiate it using Left and Right Riemann Sums, the Monte Carlo Method, the Midpoint Rule, The Trapeziod rule and Simpson's rule and changing the function would require re-doing all of these processes as well.
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Super Member Showcase_22's Avatar
    Joined
    Sep 2006
    From
    The raggedy edge.
    Posts
    782
    wow, well I have no idea how to integrate that.

    Could you just write underneath all your working "this can't be integrated" and leaving it at that?

    If you put an x as the numerator it becomes a bit easier.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Newbie
    Joined
    Aug 2008
    From
    Brisbane, Australia
    Posts
    15
    fraid not. Thanx for your help tho. I might just leave the process as is, take the loss in marks and hope that I get some for implementing the process at least partially correctly if I can't figure it out thru looking more in my text book.
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Super Member Showcase_22's Avatar
    Joined
    Sep 2006
    From
    The raggedy edge.
    Posts
    782
    Sorry about that.

    I tried it again and I can't see a way of doing it, I even tried using complex numbers!
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Newbie
    Joined
    Aug 2008
    From
    Brisbane, Australia
    Posts
    15
    Thanks a bunch anyway, I really didn't expect you to go to all of that effort to try and solve someone elses mathematical problem. I'll have to remember to let you know what the answer turns out to be if I find out.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding Area by Integration Problem.
    Posted in the Calculus Forum
    Replies: 2
    Last Post: April 25th 2010, 10:58 PM
  2. Question on integration..finding the area?
    Posted in the Calculus Forum
    Replies: 3
    Last Post: April 19th 2010, 03:05 AM
  3. finding the area using integration?
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 23rd 2010, 05:11 AM
  4. Replies: 1
    Last Post: October 19th 2009, 09:52 PM
  5. Finding area under graph by integration
    Posted in the Calculus Forum
    Replies: 1
    Last Post: November 16th 2008, 11:59 AM

Search Tags


/mathhelpforum @mathhelpforum