$$E=E_y mcosleftomega t-k x+phirightoverrightarrowa_y+E_x msinleftomega t-k x+phirightoverrightarrowa_x$$

This equation describes an electromagnetic wave in two dimensions, with electric field vectors in the y and x directions. The wave has a frequency of $\omega$, a wavenumber of $k$, and a phase angle of $\phi$. The amplitudes of the electric field vectors are $E_{ym}$ and $E_{xm}$, respectively. The wave is propagating in the direction of decreasing x, as indicated by the negative sign in front of the kx term.