I've been trying to numerically solve (and then plot) this set of equations, to reproduce results from a scientific paper (Berro et al., BPJ 2007). Maple tells me that some matrix is singular - any idea what I can do differently?

Any help much appreciated.

> eqn1 := 15*(diff(theta(s), `$`(s, 2))) = N3(s)*cos(theta(s))-N1(s)*sin(theta(s));                    ...