2 stage solution with FindRoot

*To*: mathgroup at smc.vnet.net*Subject*: [mg57416] 2 stage solution with FindRoot*From*: "mbekkali" <mbekkali at gmail.com>*Date*: Fri, 27 May 2005 04:56:55 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I have a function f[X1,X2], where X1 and X2 are vectors of variables x1[i] and x2[i], i=1,...,n. I need to solve the problem the following way. First, I need to solve for X1={X1|D[f[X1,X2],X1]==0}. Then, substituting X1 into f[.] I shall have f[X1[X2],X2]. I then need to solve for X2={X2|D[f[X1[X2],X2],X2]==0}. Since function f[.] is very complicated Solve cannot handle it. I have to use FindRoot. I know I have to use symbolic solution to a numerical function but I do not know how exactly. I tried a couple of ways but have not succeeded. Please advise. PS. I want to make it clear that I need 2 stage solution, not just 1 stage simultaneous solution to a set of 2n equations.