Question 708697
Each half would be a right isosceles triangle with both legs measuring 8 ft.
The diagonal would be the hypotenuse shared by those triangles.
We need to find the length, {{{d}}}, in feet, of that hypotenuse.
 
The Pythagorean theorem says that
the squares of the legs' lengths add up to
the squares of the length of the hypotenuse, so
{{{8^2+8^2=d^2}}} --> {{{d^2=2*8^2}}} --> {{{d=sqrt(2*8^2)}}} --> {{{d=sqrt(2)*sqrt(8^2))}}}  --> {{{highlight(d=8sqrt(2))}}}