differential equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg4522] differential equations*From*: N Kinoshita <nk204 at cam.ac.uk>*Date*: Wed, 7 Aug 1996 04:17:32 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I am a research student of economics. I want to solve a system of differential equations with Mathematica. I wrote the follwoing command based on the example given in p.698 of 'Mathematica: A system for doing mathematics by computer' ------------------------------------------------------------ ks=0.380884;cs=0.0282254;ws=0.846308; k0=ks/10; cprimess=0.00778013/0.257126; wprimess=0.966347/0.257126; NDSolve[ {c'[k]== If[k==ks,cprimess, (-0.012+0.952757k/w[k]^.7+0.11938/w[k]^.6 +2.6603c[k]/w[k]^.1-0.635171w[k]) /(0.875c[k]+0.952757k^2/w[k]^.7+1.04457k/w[k]^.6 +2.6603c[k]k/w[k]^.1-0.635171k*w[k]^.3-0.447674w[k]^.4) ], w'[k]== If[k==ks,wprimess, (1.1938w[k]^.4+6.65074c[k]w[k]^.9-1.58793w[k]^1.3) /(0.875c[k]+0.952757k^2/w[k]^.7+1.04457k/w[k]^.6 +2.6603c[k]k/w[k]^.1-0.635171k*w[k]^.3-0.447674w[k]^.4) ], c[ks]==cs, w[ks]==ws}, {c,w},{k,ks,k0}] ----------------------------------------------------------- Then I got the error message saying: NDSolve::deql: True is not a valid equation or list of valid equations. I was able to solve a single differential equation before, but do not know how to cope with my problem now. I would like to get some comments. ==== [MESSAGE SEPARATOR] ====