v 4.9

E = E_{0} \exp [i ω (t - \frac{x \cos φ + y \cos ψ + z \cos ζ}{v})]

${E = E_0 \exp \bigg[i \omega \bigg(t - \frac {x \cos \varphi + y \cos \psi + z \cos \zeta}{v}\bigg)\bigg]}$

Error