integration

Discussion in 'Math' started by micro1, Mar 22, 2015.

  1. micro1

    Thread Starter Member

    Feb 22, 2015
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    how I can complete the integration? (line integral of vector)

    2.jpg
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Well your next step should be to create two integrals.

    Have you done this

    Then it looks like a gamma function transformation integral to me, although there are (as always) other ways.

    What methods have you been taught for trig functions?

    edit presumably there should be a 'dt' in there somewhere?
     
    micro1 likes this.
  3. panic mode

    Senior Member

    Oct 10, 2011
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    and write this properly... where is dt?
     
  4. WBahn

    Moderator

    Mar 31, 2012
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    Can you integrate

    <br />
\int{u dt}<br />

    or

    <br />
\int{u^2 dt}<br />

    If so, then you are done since those are the forms you have. You just need to substitute 'u' for something in order to make it apparent.

    Note that I'm just looking at your last line. Your handwriting is too sloppy for me to be sure that I can make out your earlier stuff.
     
  5. micro1

    Thread Starter Member

    Feb 22, 2015
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    yes, dt
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    ??????
     
  7. micro1

    Thread Starter Member

    Feb 22, 2015
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    hello again
    how can do integral same wolfram ?

    Capture.PNG
     
  8. micro1

    Thread Starter Member

    Feb 22, 2015
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    respect your phrasing
     
  9. studiot

    AAC Fanatic!

    Nov 9, 2007
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    I can't see how you get from line 1 to line 2 in your original post.

    There should be six terms in line2, not two terms.

    So before you go of down some substitution route get the leadup correct.
     
  10. WBahn

    Moderator

    Mar 31, 2012
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    What makes you think I don't have respect for my phrasing?

    But let's try this: Your otherwise perfect penpersonship has been corrupted, through no fault of your own of course, by the pen, the paper, the camera, and the internet so as to make it less than optimally readable to us inferior beings.
     
  11. WBahn

    Moderator

    Mar 31, 2012
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    Could you post what you think his first line is? I can't make a good portion of it. I'm guessing the TS will be offended if I ask him to present his work more clearly.

    Like you, I don't see how the first line leads to the second, but I can't make all of that out clearly, either. It would also appear that there's a sign error in going from the second to the third, assuming that that's a plus sign between the two terms on the second line.
     
  12. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Best I can do


    \int\limits_0^{2\pi } {\left( {72\cos t\sin t - 72\sin t + 41} \right)}  \bullet \left( { - 2\sin t + 2\cos t} \right)dt

    edit corrected first bracket
     
    Last edited: Mar 23, 2015
  13. WBahn

    Moderator

    Mar 31, 2012
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    That helps. I would have never guessed that was a '41' due to what is just to the right of the '1'. I couldn't tell if that was a 'k', perhaps? It also looks like there is an 'i'-hat unit vector on the first term and maybe on the second term. Or maybe that's a 'j'-hat. Oh, wait a minute, my guess is that this is

    \int\limits_0^{2\pi } \left[ {72\cos(t)\sin(t) \hat{i} - 72\sin(t) \hat{j} + 4 \hat{k}} \right]  \cdot \left[ - 2\sin(t) + 2\cos(t) \right] dt<br />

    If so, the TS is making a total hash of things.

    So now I'm guessing that what looks like "1uH" or perhaps "1HH" on the second and third lines is actually supposed to be "144".
     
  14. studiot

    AAC Fanatic!

    Nov 9, 2007
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    yes I thought that 2x72=144.

    but you have probably hit on the meaning of the other squiggles as i,j,k
     
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