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