Can someone explain why Mathematica is doing this?

*To*: mathgroup at smc.vnet.net*Subject*: [mg19113] Can someone explain why Mathematica is doing this?*From*: belotto at vassar.edu (Benjamin Lotto)*Date*: Thu, 5 Aug 1999 01:35:30 -0400*Organization*: Vassar College*Sender*: owner-wri-mathgroup at wolfram.com

I'm running Mathematica v3.0.1.1x (or something like that) on a Macintosh. I want to replace Tan[something] with Sin[something]/Cos[something]. The obvious substitution (see below) didn't work. Other substitutions work fine, but this one just sits there. Perhaps (it has just occured to me) Mathematica is making the substitution, but then "simplifying" Sin/Cos->Tan. However, I want to make other substitutions (to check some algebra that I'm doing by hand). How can I make Mathematica do this? Thanks in advnace, -Ben In[6]:=Tan[x]/.Tan[z_]->Sin[z] Out[6]=Sin[x] In[7]:=Tan[x]/.Tan[z_]->z Sin[z] Out[7]=x Sin[x] In[8]:=Tan[x]/.Tan[z_]->Sin[z]Cos[z] Out[8]=Cos[x] Sin[x] In[9]:=Tan[x]/.Tan[z_]->Sin[z]/Cos[z] Out[9]=Tan[x] -- ------------------------------------------------------------------- Benjamin Lotto * Department of Mathematics * e-mail: belotto at vassar.edu Vassar College, Box 349 * phone: 914-437-7180 124 Raymond Avenue * fax: 914-437-7065 Poughkeepsie, NY 12604-0349 * ------------------------------------------------------------------- WWW: <http://math.vassar.edu/faculty/lotto/lotto.html> -------------------------------------------------------------------