function theta = theta(lambda_0)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                                          %
% function theta = theta(lambda_0)         %
%                                          %
% Solving 0 = theta(lambda_0) gives a      %
% candidate to initial values for lambda.  %
%                                          %
% Integrates FH(T,X) to get Z.             %
% Calculates THETA based on Z.             %
%                                          %
%                                          %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
global ti tf x0


% Integrate the differential equations
[t,z] = ode45('fh',[ti tf],[x0;lambda_0]);
z = z(length(z),:);
% WRITE STUFF BELOW
theta = [(?);           % radial speed = 0            
         (?);           % force balance  
         (?)];  	% lambda(tf) condition