Re: Why are the functions different?

*To*: mathgroup at smc.vnet.net*Subject*: [mg55642] Re: [mg55609] Why are the functions different?*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Fri, 1 Apr 2005 05:36:13 -0500 (EST)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

f1[x_]:=Normal[Series[Tanh[x],{x,0,5}]]; f0[x_]:=x-x^3/3+(2*x^5)/15; Yes they are the same when Evaluated. Further, the Help for Plot says you should Evaluate the first argument whenever possible Plot[Evaluate[{Tanh[z],f1[z]}],{z,-1,1}]; Alternatively, f2[x_]:=Evaluate[Normal[Series[Tanh[x],{x,0,5}]]]; Plot[{Tanh[z],f2[z]},{z,-1,1}]; Use ?f1 and ?f2 to look at their stored definitions. Bob Hanlon > > From: Helge Stenstroem To: mathgroup at smc.vnet.net > Date: 2005/03/31 Thu AM 01:24:00 EST > To: mathgroup at smc.vnet.net > Subject: [mg55642] [mg55609] Why are the functions different? > > How are these two functions (f0 and f1) different? f0 can be plotted, > but f1 cannot. > > f1[x_] := Normal[Series[Tanh[x], {x, 0, 5}]] > f0[x_] := x - x^3/3 + (2*x^5)/15 > > When evaluated like this: > f0[x] > f1[x] > they look the same. > > The following gives error messages if f0 is replaced by f1. > Plot[{Tanh[z], f0[z]}, {z, -1, 1}] > > (Mathematica 4.1 on Windows 2000) > -- > Helge Stenström > >