function zdot = systems_rhs( t, z )
% systems_rhs evaluates the right hand side of the ODE that is being
% solved.
% ODE23 calls this function many times when finding its numerical
% solution to the ODEs.
global C1 C2 % this matches the global command in the script file.
% The next two lines define the system of equations to be solved.
% They would be three lines for a third order system, etc.
zdot(1) = C1 *( ( z(2) ) ) ;
zdot(2) = C2 * ( - sin(z(1)) -.1*z(1) + 10* sin(t) ) ;
end % optional end statement