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Homework Help: How did Griffith check Stoke's theorem in this case?

  1. Nov 24, 2016 #1
    <Moderator's note: Moved from a technical forum, so homework template missing>

    i have one question to ask
    how to check the v.dl part in this problem
    i cannot do this problem as it is too hard to integrate the equation

    How did griffith get this long-horrible equation(see the orange circle)?
    it sounds unreasonable and too hard to get
    and is it possible that there are
    other faster ways to check the v.dl part in this problem?

    thank you

    Attached Files:

    Last edited by a moderator: Nov 24, 2016
  2. jcsd
  3. Nov 24, 2016 #2
    You can just take both integrals (one from each term in the numerator) from the table of integrals. Here's a list of integrals of irrational functions on the wiki. Or you can spend some time trying to derive those integrals yourself using the standard methods (but you don't need to do it each and every time - that's what the tables are for), as a useful exercise. Try to change the variable to some convenient trigonometric function to get rid of those square roots for starters.
    Last edited: Nov 24, 2016
  4. Nov 24, 2016 #3

    How did he prove this formula?

    Attached Files:

  5. Nov 24, 2016 #4
    What kind of integration techniques are you familiar with?
  6. Nov 24, 2016 #5
    the more simple one
    i havn't derived this formula(the two circles that i emphasize) before and not familiar with this formula
    it looks quiet tedious

    do you know what technique the Wiki is using to claim these statements

  7. Nov 24, 2016 #6
  8. Nov 24, 2016 #7
    thank you
    Khan didnt derive this formula which included x^2?
    where is these Two terms coming from

    Attached Files:

  9. Nov 24, 2016 #8
    Well, if you went through the tutorial, you should be able to derive this by yourself (the substitution is the same).
    How about you start doing this integral and show us where you get stuck?
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