Re: wrong limit ? (3)
- To: mathgroup at smc.vnet.net
- Subject: [mg76761] Re: wrong limit ? (3)
- From: dimitris <dimmechan at yahoo.com>
- Date: Sun, 27 May 2007 04:46:53 -0400 (EDT)
- References: <f38tdj$ish$1@smc.vnet.net>
An asymptotic expansion In[1]:= AsymExp1[f_, {x_, x0_, n_}] := Series[TrigToExp[f] /. E^((m_.)*x) :> y^m//Simplify, {y, x0, n}] /. y -> Exp[x] In[2]:= AsymExp1[Coth[x], {x, Infinity, 10}] Out[2]= SeriesData[E^x, Infinity, {1, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2}, 0, 11, 1] 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