The fact that the transformations changing the orientation of the light-front plane are dynamical (the corresponding generators of the Poincare group contain interaction) manifests itself in the dependence of the coefficients f 1 , 2 on the scalar product k → → ⋅ ⋅ n ^ ^ varying when the orientation of the unit vector n ^ ^ changes (for fixed k → → ). This dependence (together with the dependence on k ) is found from the dynamical equation for the wave function.