I have a question about an integral taken from integral tables of Gradshteyn and Ryzhik precisely , 3,914 -1 ( pag.490 ): http://www.lepp.cornell.edu/~ib38/tmp/reading/Table_of_Integrals_Series_and_Products_Tablicy_Integralov_Summ_Rjadov_I_Proizvedennij_Engl._2.pdf [Broken] The condition to use the result of the integral regards the real part of the two parameters . But if we do not have the real part but only imaginary part ,what we can do ? I can not find an integral which permits to overcome this difficulty. I can not understand the role of this condition, it is really necessary or in this case I can use the integral without it? Thanks to all.