Question 1193779
The square has right triangle DEC where the side is the hypotenuse. Because it is a square, the diagonals make angles EDC and ECD 45 degrees. Their lengths are sqrt(2)/2 for every 1 of the hypotenuse or their lengths are that of the hypotenuse divided by the sqrt (2).
8 sqrt (3)/sqrt(2)=8 sqrt(6)/2 after rationalizing the denominator.
This is 4 sqrt(6) and the diagonal  length is twice that or 8 sqrt (6).