9000120304

The side of a regular hexagonal prism $ABCDEF{A}^{\prime }{B}^{\prime }{C}^{\prime }{D}^{\prime }{E}^{\prime }{F}^{\prime }$ is $a=3\mathrm{cm}$ and the height $v=8\mathrm{cm}$. Find the length of the diagonal $A{D}^{\prime }$.