Transformations in expressions

*To*: mathgroup at smc.vnet.net*Subject*: [mg91874] Transformations in expressions*From*: Miguel <misvrne at gmail.com>*Date*: Thu, 11 Sep 2008 06:15:03 -0400 (EDT)

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

**Follow-Ups**:**Re: Transformations in expressions***From:*"peter lindsay" <pl.0@me.com>