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Re: Transformations in expressions

• To: mathgroup at smc.vnet.net
• Subject: [mg91911] Re: Transformations in expressions
• From: Szabolcs Horvát <szhorvat at gmail.com>
• Date: Fri, 12 Sep 2008 05:29:34 -0400 (EDT)
• Organization: University of Bergen
• References: <gaar3o$16q$1@smc.vnet.net>

Miguel wrote:
> Hi all,
> How can I to transform a specific expression to other by substitution
> of a part of it.
> 
> For example, I want to transform the expression Log[x^2+y^3]/
> Sin[x^2+y^3] in Log[z]/Sin[z] by substitution x^2+y^3 --> z.
> 

In[1]:= Log[x^2 + y^3]/Sin[x^2 + y^3] /. x^2 + y^3 -> z

Out[1]= Csc[z] Log[z]

> And other question: Is the new expression dependent of z. I see it is,
> but how can I to programar it.
> 

I don't really understand this second question ...