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MathGroup Archive 2004

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Re: Failure to Evaluate?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49845] Re: [mg49842] Failure to Evaluate?
  • From: DrBob <drbob at bigfoot.com>
  • Date: Wed, 4 Aug 2004 10:46:22 -0400 (EDT)
  • References: <200408030511.BAA00239@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

Clear[f, g, h]
f = x^2/x + 1;
g = x^4 + 7;
h[x_] = Evaluate[D[f, x]/
     D[g, x]]
h[1]

1/(4*x^3)
1/4

Clear[f, g, h]
f[x_] := x^2/x + 1
g[x_] := x^4 + 7
h[x_] := Derivative[1][f][x]/
    Derivative[1][g][x]
h[1]

1/4

Bobby

On Tue, 3 Aug 2004 01:11:14 -0400 (EDT), Scott Guthery <sguthery at mobile-mind.com> wrote:

> f:=Function[#1^2/#1+1]
>
> g:=Function[#1^4+7]
>
> h:=D[f]/D[g]
>
> h[1]
>
> Gives
>
> ((#1^2/#1)+1 &)/(#1^4+7 &)[1]
>
> Why doesn't it evaluate by setting #1 to 1 to get 1/4?
>
> h/.#1->1//N sets #1 to 1 and gives
>
> (1 1 + 1 &)/(1 + 7 &)
>
> but still doesn't evaluate to 1/4.
>
> What gives? What's the Right Stuff?
>
> Thanks for any insight.
>
> Cheers, Scott
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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