Re: Why are the functions different?

*To*: mathgroup at smc.vnet.net*Subject*: [mg55652] Re: [mg55609] Why are the functions different?*From*: Sseziwa Mukasa <mukasa at jeol.com>*Date*: Fri, 1 Apr 2005 05:36:28 -0500 (EST)*References*: <200503310624.BAA15126@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On Mar 31, 2005, at 1:24 AM, Helge Stenstroem wrote: > 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}] > Because x is evaluated before the Series and Normal in f1. Redefine f1 as f1[y_] := Block[{x}, Normal[Series[Tanh[x], {x, 0, 5}]] /.{x->y}] and it will work as you expect. Regards, Ssezi