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NDSolve and DAEs

• To: mathgroup at smc.vnet.net
• Subject: [mg124573] NDSolve and DAEs
• From: J. Jesús Rico Melgoza <jerico at umich.mx>
• Date: Wed, 25 Jan 2012 07:04:35 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Hi everybody!

I have the following DAE system:

eqns = {x1'[t] == x2[t], x2'[t] == -x3[t] - x2[t],
                                      x3'[t] == x2[t] x4[t],
                                      x4'[t] == -x3[t] x2[t]}
with initial conditions

ics = {x1[0] == 0.5, x2[0] == 0, x3[0] == Sin[0.5],
                                        x4[0] == Cos[0.5]}
that must satisfy the following constraint

x3[0]x3[0]+x4[0]x4[0]=1
The interval of time is {t,0,16}.

I do not know how to do it with NDSolve.
Can this be done? in some part of the documentation there is an example 
where the enqs are linear but the same procedure applied to my problem 
(nonlinear) wouldn't work.

I will appreciate any help.
Thanks in advance.

Best regards
Jesus Rico-Melgoza

• Follow-Ups:
  • Re: NDSolve and DAEs
    • From: Bob Hanlon <hanlonr357@gmail.com>