Dear Forum, Dear Marek Mitros, Sqrt (as a short hand for the ER cyclotomic) will only work for rational numbers. If you wanted a square root of a cyclotomic number you would need to factor x^2-a over a suitable cyclotomic field.
Best, Alexander Hulpke > On May 13, 2016, at 8:30 AM, Marek Mitros <ma...@mitros.org> wrote: > > Dear All, > > I am doing following calculation and I need square root of cyclotomic > number being real number. Here is example below. Is there any workaround > for this ? > What I am doing I obtained vector v of complex number which not unit > length. In order to normalize it I perform following and I receive the > error. Do I need more knowledge about cyclotomic numbers ? > > gap> v1:=v/Sqrt(v*ComplexConjugate(v)); > > Error, no method found! For debugging hints type ?Recovery from > NoMethodFound > > Error, no 1st choice method found for `Sqrt' on 1 arguments called from > > <function "HANDLE_METHOD_NOT_FOUND">( <arguments> ) > > (...) > > gap> n:=E(20)-E(20)^9; > > E(20)-E(20)^9 > > gap> RealPart(n); > > E(20)-E(20)^9 > > gap> Sqrt(n); > > Error, no method found! For debugging hints type ?Recovery from > NoMethodFound > > Error, no 1st choice method found for `Sqrt' on 1 arguments called from > > > Regards, > > Marek > _______________________________________________ > Forum mailing list > Forum@mail.gap-system.org > http://mail.gap-system.org/mailman/listinfo/forum _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum
