## integrate 1 / (x^2 - 1)^2

1. The problem statement, all variables and given/known data
integrate dx / (x^2 - 1)^2

2. Relevant equations

3. The attempt at a solution
There is nothing i can substitute to get rid of x. Except x=sqr(t), but then dx is 1/2sqr(t) so i get:

∫( dt / (t-1)^2 * 2sqr(t) )

and it's still impossible to integrate.

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Recognitions:
Homework Help
 Quote by aija 1. The problem statement, all variables and given/known data integrate dx / (x^2 - 1)^2 2. Relevant equations 3. The attempt at a solution There is nothing i can substitute to get rid of x. Except x=sqr(t), but then dx is 1/2sqr(t) so i get: ∫( dt / (t-1)^2 * 2sqr(t) ) and it's still impossible to integrate.
A more-or-less standard substitution to try out when you see 'x^2-1' is x = cosh(t).