function f = rigid_body( w, t )
% return the derivatives of the angular frequency for a rigid body.

Ix = 1.0;  %   moments of inertial (relative)
Iy = 2.0;
Iz = 3.0;

fx = ( (Iy-Iz)/Ix )*w(2)*w(3);
fy = ( (Iz-Ix)/Iy )*w(3)*w(1);
fz = ( (Ix-Iy)/Iz )*w(1)*w(2);

f = [ fx, fy, fz ];