The magnitude of the resultant electric field is constant (which has to be as the wave is propagating in a lossless media) but the component of electric fields along x and y are changing and hence the direction of resultant electric field is changing continuously. The resultant electric field vector E is rotating clock wise at an angular frequency , as after a time 2 the direction of electric field is same as that of starting at t=0.

From equation (2), the x component

             .......................................... (4) and y component
             ........................................... (5)