$${E_{i0} \exp \bigg[i \omega_i \bigg(t - \frac{x \cos \varphi_i}{v_1} \bigg) \bigg] + E_{r0} \exp \bigg[i \omega_r \bigg(t - \frac{x \cos \varphi_r + y \cos \psi_r}{v_1} \bigg) \bigg]= \\= E_{t0} \exp \bigg[i \omega_t \bigg(t - \frac{x \cos \varphi_t + y \cos \psi_t}{v_2} \bigg) \bigg]}$$