function [xdot] = sect_3_prob_4_J_ode_fn(t,x, alpha, T)
%   
% Written by:
% -- 
% John L. Weatherwax                2006-08-28
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

n = length(x); 
xdot = zeros(n,1); % x = [ v(t), gamma(t), h(t) ] 

v     = x(1); 
gamma = x(2); 
h     = x(3);

xdot(1) = ( T * cos( alpha ) - 32*sin( gamma ) )/(20.-t);
xdot(2) = ( T * sin( alpha ) - 32*cos( gamma ) )/((20.-t)*v);
xdot(3) = v*sin(gamma);