HELP! Why are the solutions from NDSolve and DSolve not identical?
- To: mathgroup at smc.vnet.net
- Subject: [mg37744] HELP! Why are the solutions from NDSolve and DSolve not identical?
- From: Loling Song <ls99 at cornell.edu>
- Date: Mon, 11 Nov 2002 05:09:59 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
I have, what I believe, a system of two linear, first-order,
inhomogeneous differential equations describing a real biological
system. When I tried to solve this system for a numerical solution by
NDSolve, it gave a solution that was different from that of the
symbolic solution (in which I used the same boundary conditions).
NDSolve[{y1'[t] == a y1[t] + b y2[t], y2'[t] == d + c y1[t] - b y2[t],
y1[0] == 0.0018, y2[0] == 0.03}, {y1[t], y2[t]}, {t, 0, 18000},
MaxSteps -> 1000000, AccuracyGoal -> 10, PrecisionGoal -> 10,
WorkingPrecision -> 20]
DSolve[{y1'[t] == a y1[t] + b y2[t] , y2'[t] == d + c y1[t] - b y2[t]
}, {y1[t], y2[t]}, t]
I am puzzled by these results, and would very much like to arrive at an
analytical solution. I would very much appreciate ideas and
suggestions to help me get there.
Many thanks in advance.
Loling Song
Cornell University
Department of Physics,
117 Clark Hall,
Ithaca, NY 14853
Email: LS99 at cornell.edu