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How do I compute the next integral:

$$\int \sqrt{\frac{x-1}{x+1}}\,\mathrm dx \;?$$

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1 Answer 1

up vote 4 down vote accepted

Let $\sqrt{\dfrac{x-1}{x+1}} = t$. We then get that $$\dfrac{x-1}{x+1} = t^2 \implies x-1 = t^2(x+1) \implies x = \dfrac{1+t^2}{1-t^2} \implies dx = \dfrac{4t}{(1-t^2)^2}dt$$ Hence, we get that $$\int \sqrt{\dfrac{x-1}{x+1}} dx = \int \dfrac{4t^2}{(1-t^2)^2} dt$$ I trust you can take it from here via the method of partial fractions.

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Thank you, couldn't see that trick. –  StationaryTraveller Apr 10 '13 at 17:03
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