Re: Re: Annoying Little Problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg24881] Re: [mg24865] Re: Annoying Little Problem*From*: "Tomas Garza" <tgarza at mail.internet.com.mx>*Date*: Sat, 19 Aug 2000 04:45:54 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I think perhaps it is not a matter of precision, but rather of what Mathematica prints as an answer. E.g.: In[1]:= Print[NumberForm[N[Sqrt[v2.v2]], 1]] "7." In[2]:= Print[NumberForm[N[Sqrt[v2.v2]], 2]] "7.2" In[3]:= Print[NumberForm[N[Sqrt[v2.v2]], 3]] "7.21" In[4]:= Print[NumberForm[N[Sqrt[v2.v2]], 20]] "7.211102550927978" Mathematica keeps enough precision inside, but will print only what you ask (and the default is 5). Tomas Garza Mexico City Alan [mailto:kd7cyb at mac.com] wrote: > Mathematica thinks that Sqrt[v2.v2] is sufficiently accurate enough that > the parameter specified to reduce it down to 3 digit precision is > not used; > thus, it reverts to the default 6 display digits. This is normal. Use > SetPrecision of 3 instead. N[Sqrt[v2.v2], 3] should be: > > SetPrecision[Sqrt[v2.v2],3] > > Alan > > Nalanji Dreaming wrote: > > > I'm having an annoying little problem with version 4.0.1.0. I wrote the > > following info in a notebook and ran it: > > > > Clear[v2] > > v2 = {4, 0, -6} > > N[Sqrt[v2.v2]] > > N[Sqrt[v2.v2], 3] > > > > Now the third line gives me 7.2111 but the fourth line gives me the > > same instead of 7.21. Does anyone have any idea what may be the problem? > > Am I doing something wrong? > > > > thanks, > > Nalanji Dreaming