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Definite integration

  1. Jan 6, 2012 #1
    Hi, me again,

    I'm struggling with definite integration, I have an example here in a book, but it has skipped the integration steps.

    Can some one explain to me how

    (5∏/2) ∫y8 dy = 0.873.

    I don't know how to show the numbers at the top and bottom of the integration sign these numbers are 1 at the top and 0 at the bottom.

    I tried this:

    (5∏/2) [y8] with 1 at top 0 at bottom

    (5∏/2) [1] = 7.854.

    What am I missing please?

    Regards

    Rob K
     
  2. jcsd
  3. Jan 6, 2012 #2
    [tex]\int^1_0y^8dy[/tex]
    Isn't quite [itex] y^9|^1_0[/itex]
     
  4. Jan 6, 2012 #3
    hmm, I'm a little lost, I thought 1 to the power of anything will be 1 and so I get the same answer???
     
  5. Jan 6, 2012 #4

    Mark44

    Staff: Mentor

    Like this:
    [tex]\frac{5\pi}{2}\int_0^1 y^8~dy[/tex]
    If you right-click on this expression, there's an option to show the LaTeX code, so you can see how I did it.
    You're missing an important step - finding the antiderivative of y8.
    That's wrong, too. The antiderivative of y8 is [itex]\frac{y^9}{9}[/itex]
     
    Last edited: Jan 6, 2012
  6. Jan 6, 2012 #5
    Do you know how to perform the integration?
     
  7. Jan 6, 2012 #6
    Yes yes yes, thank you, I understand now. I keep forgetting that with integration you increase the power by 1 and then divide by the new power.

    Unfortunately my integration is not good which is strange, as I find and have always found Differentiation an absolute doddle. I need to find the intuition behind maths before I understand it, I can't parrot fashion to get by. Which is a problem when you are doing an Engineering degree...

    Thanks for you help.

    Rob
     
  8. Jan 6, 2012 #7
    I know, that's why I said it wasn't quite y9
     
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