Two plane waves propagate in a homogeneous elastic medium, one along the x axis and the other along the y axis: 1 = a cos

Two plane waves propagate in a homogeneous elastic medium, one along the x axis and the other along the y axis: ε1 = a cos (wt – kx), ε2 = a cos (wt – ky) Find the wave motion pattern of particles in the plane xy if both waves.
(a) Are transverse and their oscillation directions coincide;
(b) Are longitudinal.