*To*: mathgroup@smc.vnet.net*Subject*: [mg10486] Derivative via mathematica*From*: cai <cai@iris7.cici.ohiou.edu>*Date*: Fri, 16 Jan 1998 04:35:09 -0500*Organization*: Ohio University

Hi, I just used mathematica for a couple of days. I am trying to compute the derivative under mathematica. Because the function is complicated, I like to break it down. f[t_] = (m/(1+Exp[1/t] +b) Here m and b are functions of t. If I directly use command D after insert m and b terms, a very complicated equaion is gerenated, which I do not want. What I want is if I define the values of m' and b', rewrite the f m' = p b' = q // well, I dont know how to define, this is the idea f[t_, m[t], b[t]] = (m/(1+Exp[1/t] +b) then use the command D[f[t,m[t],b[t]],t] hopeful get a equation which is the function of t, p and q. How to do that? A related question, I tried to use non-defined function In[19]:= m[t_] Out[19]= m[t_] In[20]:= D[m[t],t] Out[20]= m'[t] and expected D[f[t,m[t],b[t]],t] contains m'[t]. Is it possible? Basically, it is a chain derivative question, I just want it to stop earlier. Could somebody help? Thanks. ccai1@ohiou.edu