Re: Limit and Abs

*To*: mathgroup at smc.vnet.net*Subject*: [mg31210] Re: Limit and Abs*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Fri, 19 Oct 2001 03:12:00 -0400 (EDT)*Organization*: Universitaet Leipzig*References*: <9qjjho$j80$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, what Mathematica version ?? Mathematica 4.1 say In[]:=Limit[Abs[Cot[a]]/(Abs[Cot[a]] + 2), a -> Infinity] Out[]=1 while a picture quickly show that Abs[Cot[a]]/(Abs[Cot[a]] + 2) oscillate between 0 and 1 and the limit does not exist Your first example gives In[]:=Limit[Cot[a]/(Cot[a] + 2), a -> Infinity] Out[]=Limit[Cot[a]/(2 + Cot[a]), a -> Infinity] and finaly I would like to know what is the "correct answer" because I would assume that the limit is undefined/does not exist as to see from Plot[Cot[a]/(2 + Cot[a]), {a, 0, 100}] Regards Jens Oliver Friedrich wrote: > > Hallo, > > if I evaluate > Limit[Cot[a]/(Cot[a]+2),a->Infinity] > i get the correct answer. > > But I want to evaluate > > Limit[Abs[Cot[a]]/(Abs[Cot[a]]+2),n->Infinity] > > and that's being returned unevaluated. Help states, that Limit will return > expressions unevaluated, if there are functions with unknown behaviour (Abs > unknown ??) so I'm not too surprised or disappointed. > But anyway, how can I workaround or bypass this problem, maybe an option or > another function in the extra packages ? > > Thanks > > Oliver Friedrich