1. Nov 25, 2011 #1

   armin.hodaie

   

   1. The problem statement, all variables and given/known data
   
   ∫dr/√((1/(R+r))-(1/R))
   
   2. Relevant equations
   
   
   
   3. The attempt at a solution

    

   Last edited: Nov 25, 2011

   armin.hodaie, Nov 25, 2011
2. 
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3. Nov 25, 2011 #2

   gb7nash

   

   Homework Helper

   Is the problem [itex]\int \frac{dr}{\sqrt{(\frac{1}{R}+r)-(\frac{1}{R})}}[/itex]?
   
   If it is, try to simplify the denominator before trying to take the integral.

    

   gb7nash, Nov 25, 2011
4. Nov 25, 2011 #3

   armin.hodaie

   

   no,i type it wrong
   ∫dr/√((1/(R+r))-(1/R))

    

   armin.hodaie, Nov 25, 2011
5. Nov 25, 2011 #4

   Ray Vickson

   

   Science Advisor

   Homework Helper

   So, is your integral
   [tex] \int \frac{dr}{\sqrt{\frac{1}{R+r}-\frac{1}{R}}} ? [/tex]
   If so, re-write it by first expressing
   [tex] \frac{1}{R+r}-\frac{1}{R} [/tex]
   as a simple rational expression. You should end up with an integrand of the form
   [tex] \sqrt{\frac{ar+b}{cr+d}}. [/tex]
   
   RGV

    

   Ray Vickson, Nov 25, 2011

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