       Re: Why are the functions different?

• To: mathgroup at smc.vnet.net
• Subject: [mg55636] Re: Why are the functions different?
• From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
• Date: Fri, 1 Apr 2005 05:36:08 -0500 (EST)
• Organization: Uni Leipzig
• References: <d2g5mg\$f2m\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

you mean

f1[x_] = Normal[Series[Tanh[x], {x, 0, 5}]]
f0[x_] := x - x^3/3 + (2*x^5)/15

because if you call f1 with a numeric argument,say
x->1, you evaluate

Normal[Series[Tanh,{1,0,5}]

and this can not work. With you definition the
Series[] function
is executed in every call of f1[] and this waste
computation time.

Regards
Jens

"Helge Stenstroem"
<helge.stenstrom.NOSPAM at NOSPAMericsson.com>
schrieb im Newsbeitrag
news:d2g5mg\$f2m\$1 at smc.vnet.net...
> 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
>

```

• Prev by Date: Re: Simplifying Jacobian elliptic functions
• Next by Date: Re: Why are the functions different?
• Previous by thread: Re: Why are the functions different?
• Next by thread: Re: Why are the functions different?