function res = EulerSolve_i(t,y,yp)

    global O;
    global i;

    % y(1) = phi, y(2) = theta, y(3) = psi
    
    res = [yp(1)*sin(y(2))*sin(y(3)) + yp(2)*cos(y(3)) - O(1,i); yp(1)*sin(y(2))*cos(y(3)) - yp(2)*sin(y(3)) - O(2,i); yp(1)*cos(y(2)) + yp(3) - O(3,i)];

end