Re: Transformations in expressions

*To*: mathgroup at smc.vnet.net*Subject*: [mg91915] Re: [mg91874] Transformations in expressions*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Fri, 12 Sep 2008 05:30:18 -0400 (EDT)*Reply-to*: hanlonr at cox.net

Use ReplaceAll ( /. ) Log[x^2 + y^3]/Sin[x^2 + y^3] /. x^2 + y^3 -> z Csc[z]*Log[z] or Simplify[Log[x^2 + y^3]/Sin[x^2 + y^3], z == x^2 + y^3] csc(z) log(z) In both cases, 1/Sin[z] is automatically converted to Csc[z] as a simpler form. I do not understand your second question. Bob Hanlon ---- Miguel <misvrne at gmail.com> 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. And other question: Is the new expression dependent of z. I see it is, but how can I to programar it. Thanks -- Bob Hanlon