More problem with DSolve applied to System of ODE
- To: mathgroup at smc.vnet.net
- Subject: [mg28139] More problem with DSolve applied to System of ODE
- From: "Guillermo Sanchez" <guillerm at gugu.usal.es>
- Date: Sun, 1 Apr 2001 00:08:02 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Dear friends. I have some problems with DSolve (It is not the firt time)
in Math 4.1 for Windows. The problem is the follow:
a12 = 0.8316; a23 = 0.0086625; a31 = 0.0462; a10 = 1.9404; a30
= 0.001155;
eq = {Derivative[1][q1][t] == a1 E^(- b1*t) - (a12 + a10)*q1[t] +
a31*q3[t], Derivative[1][q2][t] == a12*q1[t] - a23*q2[t],
Derivative[1][q3][t] == a23*q2[t] - (a31 + a30)*q3[t]};
{q1[t_], q2[t_], q3[t_]} = FullSimplify[{q1[t], q2[t], q3[t]} /.
DSolve[Join[eq, {q1[0] == a, q2[0] == 0, q3[0] == 0}],
{q1[t], q2[t], q3[t]}, t][[1]] /. a -> 0];
But the solution is wrong because it doesn`t`with the initial condition.
i.e: for a1 -> 1, b1 -> 1
{q1[0], q2[0], q3[0]} /. {a1 -> 1, b1 -> 1}
out: {-0.18026427146397125, 1.327120201951776*^-16,
4.406453795543006*^-18}
that is wront It should be q1[0] = 0, and not {-0.18..}. I have test
to rationalize and increase the precition.
I will appreciate any sugestion
Guillermo Sanchez