Re: wrong limit ? (2)

*To*: mathgroup at smc.vnet.net*Subject*: [mg76803] Re: wrong limit ? (2)*From*: dimitris <dimmechan at yahoo.com>*Date*: Sun, 27 May 2007 05:08:40 -0400 (EDT)*References*: <f38tdj$ish$1@smc.vnet.net>

You could add the rule to Limit. In[1]:= Unprotect[Limit]; Limit[Coth[(a_.)*(o_)], o_ -> Infinity, Assumptions -> Element[a,Reals]] := Sign[a] Dimitris / ventu : > Hi ! > Here's my problem (mathematica 5.0,5.1,5.2): > > Limit[Coth[xB], B -> +Infinity] > > it doesn't understand. > mmh. ok I try then: > > Limit[Coth[x B], B -> +Infinity, Assumptions -> Im[x] == 0] > > 1 > > WRONG ! In fact: > > Limit[Coth[x B], B -> +Infinity, Assumptions -> Im[x] == 0 && Re[x] < > 0] > > -1 > > Indeed the correct result should be sign(x). And I couldn't find a way > to get it right. > Do I mistake something? > > Thank you in advance, > > Davide