# Homework Help: Integral solution

1. Nov 25, 2011

### 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
2. Nov 25, 2011

### gb7nash

Is the problem $\int \frac{dr}{\sqrt{(\frac{1}{R}+r)-(\frac{1}{R})}}$?

If it is, try to simplify the denominator before trying to take the integral.

3. Nov 25, 2011

### armin.hodaie

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

4. Nov 25, 2011

### Ray Vickson

$$\int \frac{dr}{\sqrt{\frac{1}{R+r}-\frac{1}{R}}} ?$$
$$\frac{1}{R+r}-\frac{1}{R}$$
$$\sqrt{\frac{ar+b}{cr+d}}.$$