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Re: how to replace with definition

• To: mathgroup at smc.vnet.net
• Subject: [mg123845] Re: how to replace with definition
• From: r_poetic <radford.schantz at mms.gov>
• Date: Thu, 22 Dec 2011 04:29:16 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201112150953.EAA22870@smc.vnet.net> <jcf813$6qk$1@smc.vnet.net>

On Dec 16, 5:54 am, Bob Hanlon <hanlonr... at gmail.com> wrote:
> k[t] = A[t]/L[t];
>
> L'[t] = lambda L[t]; A'[t] = s k[t]^alpha;
>
> D[k[t], t] /. A[t] -> HoldForm[k[t]]*L[t]
>
> % // ReleaseHold
>
> Bob Hanlon
>
>
>
>
>
> On Thu, Dec 15, 2011 at 4:53 AM,r_poetic<radford.scha... at mms.gov> wrote:
> > Hello,
> > I can't seem to manage this replacement:
>
> > k[t] = A[t]/L[t];
>
> > L'[t] = lambda L[t]; A'[t] = s k[t]^alpha;
>
> > D[k[t],t]
>
> > output=  lambda A[t] + s (A[t]/L[t]) ^ alpha
> >              -----------------     ------------------=
--=
> ---------
> >                     L[t]             =
  =
>      L[t]
>
> > How can the ratio A[t]/L[t] be replaced with k[t] here?  I have tried
> > a number of possibilities using /. or Replace.- Hide quoted text -
>
> - Show quoted text -

Thanks to all! Hold-ing works great.
RS

• References:
  • how to replace with definition
    • From: r_poetic <radford.schantz@mms.gov>