$6$ The wave equation for $E$ and $B$ from Maxwell's equations

Derive the wave equation for $E$ and $B$ from Maxwell's equations in vacuum by applying the curl to

grad$E=-\frac{\text{d}\text{e}\text{l}\text{B}}{\text{d}\text{e}\text{l}\text{t}}$

and

grad$B={}_{0}lo{n}_0\frac{\text{d}\text{e}\text{l}\text{E}}{\text{d}\text{e}\text{l}\text{t}}$

Remember that, in vacuum, grad$*E=0$ and grad$*B=0.$