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Function manipulation involving trigonometry

  1. Apr 29, 2015 #1
    I'm trying to integrate a function in a classical physics problem but when I apply the limits it gave undefined results. Hence, I looked up that particular part of the solution and I did not fathom the function manipulation. It states that if x≤b in the following expression:

    ∫{[x/b]/[1-(x/b)]}1/2 d(x/b)

    then x/b=sin2θ

    is this statement true?

    If so, how can this be?

    Thanks in advance
     
  2. jcsd
  3. Apr 29, 2015 #2

    haruspex

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    I think it is saying that if x≤b then it is valid to make that variable change. But in fact you need 0≤x/b≤1.
     
  4. Apr 29, 2015 #3
    Hi shanepitts ,
    You make make any substitution you like but, people often go through changing variable in order to make things simple, if you pose x/b = sin^2, things will become horribly complicated (at least for me) so what i suggest is making a simpler substitution, what do you think of u =sqrt(x/b) ;) ?
     
  5. Apr 29, 2015 #4

    haruspex

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    Not for me. Comes out quite simply. But this wasn't the point of the OP anyway, I think.
     
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