Services & ResourcesWolfram ForumsMathGroup Archive

[Date Index] [Thread Index] [Author Index]

Re: how to replace with definition

• To: mathgroup at smc.vnet.net
• Subject: [mg123699] Re: how to replace with definition
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Fri, 16 Dec 2011 05:44:13 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201112150953.EAA22870@smc.vnet.net>

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.schantz 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.
>

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