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Integrate[Sqrt[-a^2 + x^2]/x^3, x] ==
-Sqrt[-a^2 + x^2]/(2*x^2) - ((I/2)*Log[(4*((-I)*a + Sqrt[-a^2 + x^2]))/x])/a

                 2    2
          Sqrt[-a  + x ]
Integrate[--------------, x] == 
                 3
                x

                                         2    2
                  I     4 (-I a + Sqrt[-a  + x ])
        2    2    - Log[-------------------------]
-Sqrt[-a  + x ]   2                 x
--------------- - --------------------------------
        2                        a
     2 x