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 P: 10 Hmm, that seems to make sense, but it gets me to an integral I'm not having much more luck with. The only thing I can think of is some other subsitution that I can't figure out. $$- 2k\int {\frac{{t^8 - 4t^6 + 2(8k - 5)t^4 - 4t^2 + 1}}{{(1 + t^2 )^3 (1 - \frac{{4kt^2 }}{{(1 + t^2 )^2 }})^\frac {3}{2} }}}$$ Making $$u=1 - \frac{{4kt^2 }}{{(1 + t^2 )^2 }}$$ almost seems to work, but not quite. Any advice on what to do from here?