Using FindRoot or interpolation function with symbolic argument
- To: mathgroup at smc.vnet.net
- Subject: [mg92164] Using FindRoot or interpolation function with symbolic argument
- From: exoptery at gmail.com
- Date: Mon, 22 Sep 2008 05:26:07 -0400 (EDT)
I'd like to use NDSolve to integrate a pair of ODEs. Expressing
the system as a set of explicit equations, however, requires the
inverse of ArcTanh[x] / x. I thought I'd define a function for this
as follows:
f = Compile[{{y, _Real}}, x /. FindRoot[ArcTanh[x] == y x, {x,
99/100}]];
However, when I set, say,
eqn1 = u'[R] == u[R] f[(u[R] (1 + v[R])^2)/(1 + v[R]^2)]
Mathematica clearly dislikes the use of symbols instead of a numerical
argument.
Is there a way to define an NDSolve-digestible equation that
calls FindRoot with symbolic arguments?
Thank you for your attention.
J.