da razbira se che stava s red na taylor (macloren e chasten sluchai na reda na taylor)

eto ti oshte, obache. moje niakoe ot drugite da ti se haresa poveche..

power series
http://functions.wolfram.com/ElementaryFunctions/ArcTan/06/01/ShowAll.html

residue representation
http://functions.wolfram.com/ElementaryFunctions/ArcTan/06/02/ShowAll.html

i oshte 1
http://functions.wolfram.com/ElementaryFunctions/ArcTan/06/03/ShowAll.html