RE: Annoying Little Problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg24706] RE: [mg24701] Annoying Little Problem*From*: "Jean-Marie Thomas" <jmt at agat.net>*Date*: Wed, 9 Aug 2000 02:31:07 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Mathematica can either use your machine numerical function OR if more precision is required, its own. N is a numerical evaluation function. Then if you evaluate v={4, 0, -6} N[Sqrt[v.v}] will compute a numerical evaluation of Sqrt[v.v] See : N[Sqrt[v.v}]//FullForm to view the internals. If you evaluate N[Sqrt[v.v},3], Mathematica will keep using the standard numerical function. See N[Sqrt[v.v},3]//FullForm to view the internals. N[Sqrt[v.v],64] will increase the precision. If you need a formatting function, use NumberForm : NumberForm[N at Sqrt[v.v], {3, 2}] 7.21 > -----Message d'origine----- > De : Nalanji Dreaming [mailto:ayrton at rac1.wam.umd.edu] > Envoyé : vendredi 4 août 2000 07:19 > À : mathgroup at smc.vnet.net > Objet : [mg24701] Annoying Little Problem > > > 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