Re: transforming exponential of sums into product of exponentials

• To: mathgroup at smc.vnet.net
• Subject: [mg48689] Re: [mg48654] transforming exponential of sums into product of exponentials
• From: DrBob <drbob at bigfoot.com>
• Date: Thu, 10 Jun 2004 02:44:19 -0400 (EDT)
• References: <200406090817.EAA15676@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Use RuleDelayed, and you get a bit farther. Evaluate these lines to see what I mean:

Trace[Exp[x + y] /. Exp[a_ + b_] -> Exp[a]Exp[b]]
Trace[Exp[x + y] /. Exp[a_ + b_] :> Exp[a]Exp[b]]

The second method makes the transformation you want, but the work is undone by an automatically applied rule.

This may do what you want:

Exp[x + y] /. Exp[(a_) + (b_)] :> HoldForm[Exp[a]*Exp[b]]
HoldForm[E^x*E^y]

Bobby

> Dear All,
>
> I can not understand why Mathmatica refuses to apply rules which transform
> exponenials of sums into product of exponentails.
>
> For instance,
> f[x+y] /. f[a_ + b_]-> f[a] f[b] returns f[x] f[y],
> whereas
> Exp[x+y] /. Exp[a_+b_]->Exp[a]Exp[b] still returns Exp[x+y]
>
> Any help greatly appreciated
>
>
>
>
>
>

--
DrBob at bigfoot.com
www.eclecticdreams.net/index.html

```

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