Re: Some problems with DSolve and NDSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg19836] Re: Some problems with DSolve and NDSolve*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sun, 19 Sep 1999 01:20:23 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Hi, > > The problem is that NDSolve can handle only explicit systems of differential > equations, i.e. ODE's of the form > > (x1', x2', ..., xn') == f(x1, x2, ..., xn), > > but your equations are given in implicit form: > > f(x1, x2, ..., xn, x1', x2', ..., xn') == 0 That is simply not true. NDSolve can handle implicit equations as long as the coefficient matrix is not singular. But *this* is exact the case here. Replace *one* of the i1'[t]-i2'[t] terms in the equations by i1'[t]+i2'[t] (the quations are still implicit) but now Solve[_,{i1'[t],i2't]}] can transform it to the explicit form. Regards Jens