Question 878055
What does "route 3" mean? Do you mean "root 3"
If you mean {{{8 sqrt(3)}}} you should say so.

If a side is 8
the base is 8
we want half of the base which is 4
so we have
 8^2=4^2+a^2
64=16+a^2
48=a^2
a=6.9282032302755091741097853660235
If you mean  {{{8 sqrt(3)}}} 
{{{8 sqrt(3)}}}^2=({{{4 sqrt(3)}}})^2+a^2
64*3=16*3+a^2
192=48+a^2
144=a^2
a=12